Aqueous polyurethane coating compositions

ABSTRACT

An aqueous coating composition comprising a crosslinkable water-dispersible polyurethane oligomer wherein said composition when drying to form a coating has an open time of at least 20 minutes, a wet-edge time of at least 10 minutes, a tack free time of &lt;20 hours and an equilibrium viscosity of &lt;5,000 Pa·s at a solids content when drying in the range of from 20 to 55 wt % using a shear rate in the range of from 9±0.5 to 90±5 s −1  and at 23+2° C.

The present invention relates to certain aqueous ambient temperaturecrosslinkable and shelf stable polyurethane polymer compositions which,inter alia, provide coatings having improved open and wet edge times aswell as good tack-free times.

A general need when applying a decorative or protective coating to asubstrate is to be able to repair irregularities in the still-wetcoating after some time has elapsed, for example by re-brushing over afreshly coated wet substrate, or by applying more of the coatingcomposition over a previously coated substrate either over the main areaof the coating or an edge of the coating or even blending a drop intothe coating without in each case vitiating the complete merging of anyboundaries in the vicinity of the repaired irregularity. Traditionallycompositions containing binder polymers dissolved in organic solventsare used and the organic solvents are employed to modify the dryingcharacteristics of the coated composition. For example, organic solventbased alkyds with an open time of 30 to 45 minutes are available in thedecorative “Do-it-Yourself” DIY market. However the disadvantage oforganic solvent based coatings is the toxic and flammable nature of suchsolvents and the pollution and odour caused on evaporation as well asthe relatively high cost of organic solvents.

Thus with the continuing concern about the use of organic solvent basedcoating compositions there has been a long felt need for an aqueouscoating composition with comparable properties to those achievable usingorganic solvent based compositions.

Unfortunately, aqueous polymer coating compositions currently known tothe art do not offer a combination of drying properties which would makethem fully comparable (or even superior to) solvent-based coatings, andin particular do not provide desirably long open and wet edge times (asdiscussed above and also later) together with desirably short tack-freetimes (discussed later).

Thus, very commonly, aqueous-based polymer coating compositions employdispersed high molecular weight polymers as the binder materialsthereof. This results in, inter alia, a short wet edge time when thecoating composition is dried because the dispersed polymer particlestend to coalesce in the edge region of an applied coating very soonafter a wet coating has been applied (probably due to the maximumpacking fraction of the polymer particles having been reached) to form acontinuous film, and since the polymer of this film is of high viscositybecause of its highly molecular weight, the lapping (i.e. wet edge) timeof the composition is poor.

It has been shown by viscosity measurements taken during drying thatexisting alkyd emulsions have a high viscosity phase inversion peakduring drying. (Phase inversion is defined as the transition from abinder in a continuous water phase to water in a continuous binder phasewhich occurs during drying). The consequence is a difficulty inre-brushing which starts a few minutes after application of the coating.

It is known from the prior art that longer wet edge or open time isachievable by using solution-type aqueous oligomers (U.S. Pat. No.4,552,908) which can be diluted with large amounts of organic solvent(s)in order to create a low viscosity continuous phase during drying of thefilm. However, these systems have high Volatile Organic Contents (VOC's)and are generally unacceptably water-sensitive.

Open time can also be prolonged by using evaporation suppressants (suchas e.g. eicosanol), as described in for example EP 210747. However,water sensitivity is also a problem in this case. Moreover, the wet edgeopen time is insufficiently improved by using such evaporationsuppressants.

From the literature it is also known that open time is easily prolongedby using low solids contents in the aqueous polymer compositions, butthis generally results in the need to apply many layers of paint (forgood opacity). In addition, the wet edge time is generally onlymoderately influenced by reducing the solids content of an aqueouscoating composition with water.

Longer times for repairing irregularities can be achieved by employingaqueous polymer coating compositions in which the binder polymers havevery low viscosities. However, hitherto, a problem with using such lowviscosity polymer binders, is that the resultant coatings have a slowdrying rate, resulting in the coating remaining tacky for anunacceptably long time. A coating should preferably also drysufficiently quickly to avoid the adherence of dust and to ensure thatthe coating quickly becomes waterproof (in case of outdoorapplications), and, as discussed above, quickly becomes tack-free.

Indeed, the difficulty in developing aqueous polymer coatingcompositions having a desirable combination of drying properties whencoated onto a substrate has been particularly discussed in a recentinterview given by Professor Rob van der Linde (Professor of CoatingsTechnology, University of Technology, Eindhoven, NL) and Kees van derKolk (Sigma Coatings) and reported in “Intermediair” Oct. 6, 1999,35(23), pages 27-29. In this interview, concerning environmentallyfriendly paints, there is described the problem of applying aqueouspaints where even the professional painter has little enough time tocorrect any irregularities when needed. This is contrasted (in theinterview) with solvent-based paints (e.g. alkyd paints) which areworkable for a much longer time but have the disadvantage that theorganic solvents, forming a major component of such compositions, aretoxic and expensive. The interview also mentions that in the comingyears, three universities will cooperate in a project to overcome thedrying disadvantages of aqueous paints. Thus this interview emphasisesthe current and continuing need and desirability for achieving aqueouspolymer coatings compositions having improved drying properties.

The open time for a coating composition is, in brief, the period of timethat the main area (the bulk) of an applied aqueous coating remainsworkable after it has been applied to a substrate, in the sense thatduring this period re-brushing or application of more coating over themain area of a freshly coated wet substrate is possible without causingdefects such as brush marks in the final dried coating. (A more formaldefinition of open time is provided later in this specification).

The wet edge time for a coating composition is, in brief, the period oftime that the edge region of an applied aqueous coating remains workableafter it has been applied to a substrate, in the sense that during thisperiod re-brushing or application of more coating over the edge regionof a freshly coated wet substrate is possible without causing defectssuch as lap lines in the final dried coating. (A more formal definitionof wet edge time is provided later in this specification).

U.S. Pat. No. 5,104,707, U.S. Pat. No. 5,039,732 and WO 00/27938disclose the preparation of uralkyd modified polyurethanes and WO00/24837 discloses a polyurethane/acrylate dispersion blended with apolyurethane with oxidatively drying groups; however the maximum opentime was only 7 minutes, and, in particular, a wet edge time of only 4minutes was achieved, neither of which is sufficient for most decorativepurposes.

U.S. Pat. No. 4,552,908 describes a solids/viscosity relationship ofoligomers with defined molecular weight upon drying coatings appliedfrom compositions containing the oligomers. The compositions have >10minutes wet edge time, but there is no mention that the oligomers arecrosslinkable (an important feature of the present invention, seelater). All oligomers mentioned in the patent are very water-sensitive.

We have now invented aqueous polymer coating compositions having a veryadvantageous combination of drying properties, particularly with regardto open time, wet edge time and tack-free time as discussed above, andwhich (surprisingly in view of the comments by van der Linde and van derKolk) avoid the drawbacks of the currently available compositions.

According to the present invention there is provided an aqueous coatingcomposition comprising a crosslinkable water-dispersible polyurethaneoligomer(s) wherein said composition when drying to form a coating hasthe following properties:

i) an open time of at least 20 minutes;

ii) a wet-edge time of at least 10 minutes;

iii) a tack-free time of ≦20 hours;

iv) 0 to 25% of co-solvent by weight of the composition; and

v) an equilibrium viscosity of ≦5,000 Pa·s, at any solids content whendrying in the range of from 20 to 55% by weight of the composition,using any shear rate in the range of from 9±0.5 to 90±5 s⁻¹ and at 23±2°C.

Open time is more formally defined as the maximum length of time, usingthe test method and under the specified conditions described later, inwhich a brush carrying the aqueous composition of the invention can beapplied to the main area of a coating of the aqueous composition of theinvention after which the coating flows back so as to result in ahomogenous film layer.

Preferably the open time is at least 25 minutes, more preferably atleast 30 minutes and most preferably at least 35 minutes.

Wet edge time is more formally defined as the maximum length of time,using the test method under the specified conditions described herein,in which a brush carrying the aqueous composition of the invention canbe applied to the edge region of a coating of the aqueous composition ofthe invention after which the coating flows back without leaving any laplines in the final dried coating, so as to result in a homogenous filmlayer.

Preferably the wet-edge time is at least 12 minutes, more preferably atleast 15 minutes, most preferably at least 18 minutes and especially atleast 25 minutes.

The drying process of an applied invention composition can be divided infour stages namely the periods of time necessary to achieverespectively, dust-free, tack-free, sandable and thumb-hard coatingsusing the tests described herein.

Preferably the dust free time is ≦4 hours, more preferably ≦2 hours andstill more preferably ≦50 minutes.

Preferably the tack-free time is ≦15 hours, more preferably ≦12 hoursand still more preferably ≦8 hours.

Preferably the thumb hard time is ≦48 hours, more preferably ≦24 hours,more preferably less than 16 hours and especially ≦10 hours.

Preferably the resultant coating is sandable within 72 hours, morepreferably within 48 hours, still more preferably within 24 hours andespecially within 16 hours.

A co-solvent, as is well known in the coating art, is an organic solventemployed in an aqueous composition to improve the drying characteristicsthereof. The co-solvent may be solvent incorporated or used duringpreparation of the polyurethane oligomer(s) or may have been addedduring formulation of the aqueous composition.

The equilibrium viscosity of the aqueous coating composition whenmeasured under the conditions, as described above, is a suitable methodfor illustrating the drying characteristics of the aqueous coatingcomposition. By the equilibrium viscosity of an aqueous composition at aparticular shear rate and solids content is meant the viscosity measuredwhen the aqueous composition has been subjected to the shear rate at forlong enough to ensure that the viscosity measurement has reached aconstant value.

If the composition is to remain brushable and workable during drying sothat it has the desired open time and wet edge time, it is necessarythat its equilibrium viscosity does not exceed defined limits during thedrying process and hence over a range of solids contents. Accordinglythe crosslinkable water-dispersible polyurethane oligomer(s) which areused in this invention do not give a significant phase inversionviscosity peak, if any at all, during the drying process when the systeminverts from one in which water is the continuous phase to one in whichthe crosslinkable water-dispersible polyurethane oligomer(s) is thecontinuous phase.

The shear rate to measure the equilibrium viscosity is preferably anyshear rate in the range of from 0.9±0.05 to 90±5 s⁻¹, more preferablyany shear rate in the range of from 0.09±0.005 to 90±5 s⁻¹.

Preferably the equilibrium viscosity of the aqueous coating compositionof the invention is ≦3000 Pa·s, more preferably ≦1500 Pa·s, still morepreferably ≦500 Pa·s, especially ≦100 Pa·s, and most especially ≦50 Pa·swhen measured as defined above.

Preferably, the composition of the invention has an equilibriumviscosity ≦5,000 Pa·s when measured using any shear rate in the range offrom 0.09±0.005 to 90±5 s⁻¹, and an equilibrium viscosity of ≦3,000 Pa·swhen measured using any shear rate in the range of from 0.9±0.05 to 90±5s⁻¹, and an equilibrium viscosity of ≦1,500 Pa·s when measured using anyshear rate in the range of from 9±0.5 to 90±5 s⁻¹, at any solids contentwhen drying in the range of from 20 to 55% by weight of the compositionand at 23±2° C.

More preferably, the composition of the invention has an equilibriumviscosity of ≦3,000 Pa·s when measured using any shear rate in the rangeof from 0.09±0.005 to 90±5 s⁻¹, and an equilibrium viscosity of ≦1,500Pa·s when measured using any shear rate in the range of from 0.9±0.05 to90±6 s⁻¹, and an equilibrium viscosity of ≦500 Pa·s when measured usingany shear rate in the range of from 9±0.5 to 90±5 s⁻¹, at any solidscontent when drying in the range of from 20 to 55% by weight of thecomposition and at 23±2° C.

Even more preferably, the composition of the invention has anequilibrium viscosity of ≦1,500 Pa·s when measured using any shear ratein the range of from 0.09±0.005 to 90±5 s⁻¹, and an equilibriumviscosity of ≦200 Pa·s when measured using any shear rate in the rangeof from 0.9±0.05 to 90±5 s⁻¹, and an equilibrium viscosity of ≦100 Pa·swhen measured using any shear rate in the range of from 9±0.5 to 90±5s⁻¹, at any solids content when drying in the range of from 20 to 55% byweight of the composition and at 23±2° C.

Preferably the solids content of the aqueous coating composition whendetermining the equilibrium viscosity is in the range of from 20 to 60%,more preferably in the range of from 20 to 65%, still more preferably inthe range of from 20 to 70%, especially in the range of from 20 to 75%by weight of the composition.

Preferably the equilibrium viscosity of the composition of the inventionis ≦5000 Pa·s, more preferably ≦3000 Pa·s when measured using any shearrange in the range of from 0.9±0.05 to 90±5 s⁻¹, more preferably usingany shear rate in the range of from 0.09±0.005 to 90±5 s⁻¹; after a 12%,preferably a 15% and most preferably an 18% increase in the solidscontent by weight of the composition when drying (e.g a 12% increasemeans going from a solids content of 35 to 47% by weight of thecomposition).

In a preferred embodiment of the present invention said polyurethaneoligomer(s) has a solution viscosity ≦150 Pa·s, as determined from a 80%by weight solids solution of the crosslinkable polyurethane oligomer(s)in at least one of the solvents selected from the group consisting ofN-methylpyrrolidone, n-butylglycol and mixtures thereof, using a shearrate of 90±5 s⁻¹ and at 50±2° C.

A choice of solvents for determining the solution viscosity of thepolyurethane oligomer(s) is provided herein because the nature of thepolyurethane oligomer(s) may affect its solubility.

Preferably the solution viscosity of the crosslinkable polyurethaneoligomer(s) is ≦100 Pa·s, especially ≦50 Pa·s and most especially ≦30Pa·s when measured as defined above.

Alternatively in this embodiment of the invention, and more preferably,the solution viscosity of the polyurethane oligomer(s) may be measuredat 23±2° C., and the crosslinkable polyurethane oligomer(s) may thusalso be described as preferably having a solution viscosity ≦250 Pa·s,as determined from a 70% by weight solids solution of the crosslinkablepolyurethane oligomer(s) in a solvent mixture consisting of:

i) at least one of the solvents selected from the group consisting ofN-methylpyrrolidone, n-butylglycol and mixtures thereof;

ii) water and

iii) N,N-dimethylethanolamine;

where i), ii) and iii) are in weight ratios of 20/7/3 respectively,using a shear rate of 90±5 s⁻¹ and at 23±2° C.

Preferably in the preceding alternative the solution viscosity of thecrosslinkable polyurethane oligomer(s) is ≦100 Pa·s, more especially ≦50Pa·s, still more especially ≦35 Pa·s and most especially ≦20 Pa·s, whenmeasured as defined herein at 23±2° C.

If a mixture of N-methylpyrrolidone (NMP) and n-butylglycol (BG) isused, preferably the ratio of NMP:BG is in the range of from 0.01:99.9to 99.9:0.01, more preferably the ratio of NMP:BG is in the range offrom 0.01:99.9 to 10:90 and in the range of from 90:10 to 99.9:0.01, andmost preferably the ratio of NMP:BG is in the range of from 0.5:99.5 to5:95 and in the range of from 95:5 to 99.5:0.5.

In a special embodiment of the present invention the wet edge time inminutes of the aqueous coating composition is at least Q/(wt. % solidsof the aqueous coating composition)^(0.5), wherein the solids content ofthe aqueous coating composition is between 15 and 70 wt. %, morepreferably between 30 and 65 wt. % and most preferably between 40 and 60wt. % and Q is a constant of 84, more preferably of 100, most preferablyof 126 and especially of 151.

The crosslinkable polyurethane oligomer(s) may crosslink at ambienttemperature by a number of mechanisms including but not limited toautoxidation, Schiff base crosslinking and silane condensation. Bycrosslinking by autoxidation is meant that crosslinking results from anoxidation occurring in the presence of air and usually involves a freeradical mechanism and is preferably metal-catalysed resulting incovalent crosslinks. By Schiff base crosslinking is meant thatcrosslinking takes place by the reaction of a carbonyl functionalgroup(s), where by a carbonyl functional group herein is meant an aldoor keto group and includes an enolic carbonyl group such as is found inan acetoacetyl group with a carbonyl-reactive amine and/or hydrazine (orblocked amine and/or blocked hydrazine) functional group. Examples ofcarbonyl-reactive amine (or blocked amine) functional groups includeones provided by the following compounds or groups: R—NH₂, R—O—NH₂,R—O—N═C<, R—NH—C(═O)—O—N═C< and R—NH—C(═O)—O—NH₂ where R is optionallysubstituted C₁ to C₁₅ preferably C₁ to C₁₀ alkylene, optionallysubstituted alicyclic or optionally substituted aryl or R may also bepart of a polymer. Examples of carbonyl-reactive hydrazine (or blockedhydrazine) compounds or groups include R—NH—NH₂, R—C(═O)—NH—NH₂,R—C(═O)—NH—N═C<, R—NH—C(═O)—NH—NH₂ and R—NH—C(═O)—NH—N═C< where R is asdescribed above. By silane condensation is meant the reaction of alkoxysilane or —SiOH groups in the presence of water, to give siloxane bondsby the elimination of water and/or alkanols (for example methanol)during the drying of the aqueous coating composition.

Preferably the crosslinkable polyurethane oligomer(s) is aself-crosslinkable polyurethane oligomer(s) (i.e. crosslinkable withoutthe requirement for added compounds which react with groups on thepolyurethane oligomer(s) to achieve crosslinking—although these canstill be employed if desired). Preferably the crosslinking is byautoxidation, optionally in combination with other crosslinkingmechanisms as discussed herein. Suitably autoxidation is provided forexample by fatty acid groups containing unsaturated bonds (by which ismeant the residue of such fatty acids which have become incorporatedinto the polyurethane oligomer by reaction at their carboxylic acidgroups) or by (meth)allyl functional residues, β-keto ester groups orβ-keto amide groups. Preferably autoxidation is provided at least byfatty acid groups containing unsaturated bonds.

Preferably the concentration of unsaturated fatty acid groups if presentin the autoxidisably crosslinkable polyurethane oligomer(s) is 10 to80%, more preferably 12 to 70%, most preferably 15 to 60% by weightbased on the weight of the polyurethane oligomer(s). If combined withother autoxidisable groups in the aqueous coating composition, the fattyacid content may more readily be below 10% by weight of the polyurethaneoligomer(s). For the purpose of determining the fatty acid group contentof the polyurethane oligomer(s), it is convenient for practical purposesto use the weight of the fatty acid reactant including the carbonylgroup but excluding the hydroxyl group of the terminal acid group of thefatty acid. Suitable unsaturated fatty acids for providing fatty acidgroups in the oligomer(s) include fatty acids derived from vegetable oilor non-vegetable oil such as soyabean oil, palm oil, linseed oil, tungoil, rapeseed oil, sunflower oil, tallow oil, (dehydrated) castor oil,safflower oil and fatty acids such as linoleic acid, linolenic acid,palmitoleic acid, oleic acid, eleostearic acid, licanic acid,arachidonic acid, ricinoleic acid, erucic acid, gadoleic acid,clupanadonic acid and/or combinations thereof. Particularly preferred isa polyurethane oligomer(s) in which the autoxidisable groups are onlyderived from unsaturated fatty acids. Preferably at least 40% by weight,more preferably at least 60% by weight, of the unsaturated fatty acidgroups contain at least two unsaturated groups.

Other crosslinking mechanisms known in the art include those provided bythe reaction of epoxy groups with amino, carboxylic acid or mercaptogroups, the reaction of mercapto groups with ethylenically unsaturatedgroups such as fumarate and acryloyl groups, the reaction of maskedepoxy groups with amino or mercapto groups, the reaction ofisothiocyanates with amines, alcohols or hydrazines, the reaction ofamines (for example ethylenediamine or multifunctional amine terminatedpolyalkylene oxides) with β-diketo (for example acetoacetoxy oracetoamide) groups to form enamines. The use of blocked crosslinkinggroups may be beneficial.

The crosslinkable polyurethane oligomer(s) preferably contains asufficient concentration of bound hydrophilic water-dispersing groupscapable of rendering the oligomer(s) self-water-dispersible (i.e.dispersible in water without the requirement to use added dispersingagents) but the concentration of such groups is preferably not so greatthat the oligomer(s) has an unacceptably high water solubility in orderto not compromise the water sensitivity of the final coating.

The type of hydrophilic groups capable of rendering the crosslinkablepolyurethane oligomer(s) self-water-dispersible are well known in theart, and can be ionic water-dispersing groups or non-ionicwater-dispersing groups. Preferred non-ionic water-dispersing groups arepolyalkylene oxide groups, more preferably polyethylene oxide groups. Asmall segment of the polyethylene oxide group can be replaced bypropylene oxide segment(s) and/or butylene oxide segment(s), however thepolyethylene oxide group should still contain ethylene oxide as a majorcomponent. When the water-dispersible group is polyethylene oxide, thepreferred ethylene oxide chain length is >4 ethylene oxide units,preferably >8 ethylene oxide units and most preferably >15 ethyleneoxide units. Preferably the polyethylene oxide group has a Mw from 175to 5000 Daltons, more preferably from 350 to 2200 Daltons, mostpreferably from 660 to 2200 Daltons. Preferably the polyurethaneoligomer(s) has a polyethylene oxide content of 0 to 45% by weight, morepreferably 0 to 30% by weight and most preferably 2 to 20% by weight.

Preferred ionic water-dispersing groups are anionic water-dispersinggroups, especially carboxylic, phosphoric and or sulphonic acid groups.The anionic water-dispersing groups are preferably fully or partially inthe form of a salt. Conversion to the salt form is optionally effectedby neutralisation of the crosslinkable polyurethane oligomer(s) with abase, preferably during the preparation of the crosslinkablepolyurethane oligomer(s) and/or during the preparation of thecomposition of the present invention. The anionic dispersing groups mayin some cases be provided by the use of a monomer having an alreadyneutralised acid group in the polyurethane oligomer(s) synthesis so thatsubsequent neutralisation is unnecessary. If anionic water-dispersinggroups are used in combination with non-ionic water-dispersing groups,neutralisation may not be required.

If the anionic water-dispersing groups are neutralised, the base used toneutralise the groups is preferably ammonia, an amine or an inorganicbase. Suitable amines include tertiary amines, for example triethylamineor N,N-dimethylethanolamine. Suitable inorganic bases include alkalihydroxides and carbonates, for example lithium hydroxide, sodiumhydroxide, or potassium hydroxide. A quaternary ammonium hydroxide, forexample N⁺(CH₃)₄OH⁻, can also be used. Generally a base is used whichgives counter ions that may be desired for the composition. For example,preferred counter ions include Li⁺, Na⁺, K⁺, NH₄ ⁺ and substitutedammonium salts.

Cationic water dispersible groups can also be used, but are lesspreferred. Examples include pyridine groups, imidazole groups and orquaternary ammonium groups which may be neutralised or permanentlyionised (for example with dimethylsulphate).

The crosslinkable polyurethane oligomer(s) preferably has a measuredweight average molecular weight (Mw) in the range of from 1000 to 80,000Daltons, more preferably in the range of from 1500 to 50,000 Daltons,and most preferably in the range of from 1500 to 20,000 Daltons. Atypical range is from 1500 to 10,000 Daltons. For the purpose of thisinvention any molecular species with a molecular weight <1000 Daltons isclassified as either a reactive diluent or plasticiser and is thereforenot taken into account for the determination of Mn, Mw or PDi. Daltonsas used herein are not a true molecular weight but a molecular weightmeasured against polystyrene standards as described below.

For polyurethane oligomer(s) with a low level of intermolecularinteractions, like for example polyurethane oligomer(s) based onα,α′-tetramethylxylene diisocyanate (TMXDI) and preferably low levels ofother hydrogen bridging groups like carboxylic acid groups, the higherMw ranges are valid.

For polyurethane oligomer(s) with a high level of intermolecularinteractions, like for example polyurethane oligomer(s) based onaromatic isocyanates with relatively higher levels of hydrogen bridginggroups, the lower Mw ranges are most suitable.

Preferably a significant part of any crosslinking reaction only takesplace after application of the aqueous coating composition to asubstrate, to avoid an excessive molecular weight build up in theinvention composition prior to such application (by precrosslinking)which may lead to unacceptably increased viscosity of the aqueouscoating composition on the substrate in the early stages of drying.

The molecular weight limits suitable to obtain the preferred lowsolution viscosity of the crosslinkable polyurethane oligomer(s) (asdefined above) depend in part on the amount and type of co-solvent ifpresent in the aqueous composition of the invention. Thus a highermolecular weight limit is preferred when there is more co-solvent in thecomposition, and the lower molecular weight preferences are moreapplicable to low or zero co-solvent concentrations. Furthermore if abranched polyurethane oligomer(s) is used, higher molecular weightlimits are preferred as branched structures tend to give a lowerviscosity than a linear structure for any given Mw.

The molecular weight distribution (MWD) of the crosslinkablepolyurethane oligomer(s) has an influence on the equilibrium viscosityof the aqueous composition of the invention, and hence an influence onthe open time. MWD is conventionally described by the polydispersityindex (PDi). PDi is defined as the weight average molecular weightdivided by the number average molecular weight (Mw/Mn) where lowervalues are equivalent to lower PDi's. It has been found that a lower PDioften results in lower viscosities for a given Mw crosslinkablepolyurethane oligomer(s). Preferably the value of PDi for an aliphaticpolyurethane oligomer(s) is ≦15, more preferably ≦10, and mostpreferably ≦5. In a preferred embodiment the value of Mw×PDi^(0.8) ofthe crosslinkable polyurethane oligomer(s) is ≦400,000, more preferablythe Mw×PDi^(0.8) is ≦300,000 and most preferably the Mw×PDi^(0.8) is≦220,000.

The crosslinkable polyurethane oligomer(s) may comprise a singlecrosslinkable polyurethane oligomer or a mixture of crosslinkablepolyurethane oligomers. The crosslinkable polyurethane oligomer(s) mayoptionally be used in conjunction with a crosslinkable oligomer(s) of anon-polyurethane type which has a solution viscosity within the samepreferred limits as the solution viscosity of the polyurethaneoligomer(s). Indeed up to 90% by weight of crosslinkable oligomer(s) inthe invention composition may be of a non-polyurethane type. Thecrosslinkable oligomer(s) (polyurethane type plus, if present,non-polyurethane type) may optionally be used in conjunction with up to250% by weight thereof of any type of non-crosslinkable oligomer (i.e.polyurethane and/or non-polyurethane type) provided that thenon-crosslinkable oligomer(s) has a solution viscosity within thepreferred ranges defined above for the solution viscosity of thecrosslinkable polyurethane oligomer(s). In such cases, more preferablyup to 120 wt % of the non-crosslinkable oligomer(s) (based on the weightof crosslinkable oligomer(s)) is used, more preferably up to 30 wt %,more preferably up to 10%, and most preferably 0%. Oligomer(s) of anon-polyurethane type include but are not limited to for example vinyloligomer(s), polyamide oligomer(s), polyether oligomer(s), polysiloxaneoligomer(s) and/or polyester oligomer(s) and the non-polyurethane typeoligomer(s) may optionally be branched.

Methods for preparing polyurethanes are known in the art and aredescribed in for example the Polyurethane Handbook 2^(nd) Edition, aCarl Hanser publication, 1994, by G. Oertel; and these methods areincluded herein by reference. The polyurethane oligomer(s) may beprepared in a conventional manner by reacting an organicpolyisocyanate(s) with an isocyanate-reactive compound(s) by methodswell known in the prior art. Isocyanate-reactive groups include —OH,—SH, —NH—, and —NH₂. In some preparations, an isocyanate-terminatedpolyurethane prepolymer is first formed which is then chain extendedwith an active hydrogen containing compound.

Crosslinkable polyurethane oligomer(s) containing crosslinker groups arepreferably obtained by employing as a reactant in the urethane synthesisat least one isocyanate-reactive organic compound bearing a crosslinkergroup(s). Alternatively, but less preferably, an isocyanate functionalcompound bearing a crosslinker group(s) may be used. Polymer-boundhydrophilic water-dispersing groups, if present, are preferablyintroduced by employing as a reactant(s) in the urethane synthesis atleast one isocyanate-reactive compound (or less preferably anisocyanate-functional compound(s)) bearing a hydrophilic dispersinggroup(s). Optionally, the reactants may also include isocyanate-reactivecompound(s) such as organic polyol(s) bearing neither crosslinker groupsnor hydrophilic water-dispersing groups.

A polyurethane oligomer(s) of acceptably low Mw may be made by cappingan isocyanate-terminated polyurethane oligomer(s) with a monofunctionalisocyanate-reactive compounds or by using a stoichiometric excess ofreactant(s) having isocyanate-reactive groups during the oligomerpreparation, thereby forming an isocyanate-reactive group (preferably—OH) terminated polyurethane oligomer. A combination of both techniquesmay be used.

When employing the prepolymer/chain extension route to form apolyurethane, an isocyanate-reactive organic compound bearingcrosslinker groups may be introduced on the polyurethane oligomerbackbone during the prepolymer formation and/or during the chainextension step.

Optionally, as mentioned above, isocyanate-reactive organic compoundsbearing hydrophilic water-dispersing groups may be included in thepolyurethane oligomer formation to provide the facility ofself-dispersability in water of the crosslinkable polyurethaneoligomer(s) and methods analogous to those for introducing crosslinkergroups may be used (i.e. employing isocyanate-reactive orisocyanate-functional compounds bearing water-dispersing groups ratherthan crosslinker groups).

The crosslinker or water-dispersing groups may in fact be introducedinto the polyurethane oligomer(s) using two general methods: i) (beingthe method which is most used) by utilising in the polymerisationprocess to form a polyurethane oligomer a polyfunctional and/ormonofunctional compound carrying a crosslinker or water-dispersinggroup; or ii) (less often used) utilising a reactant in the urethanesynthesis a compound bearing a selected reactive group, and subsequentlyreacting the precursor oligomer so formed with a compound carrying acrosslinker or water-dispersing group and also a reactive group of thetype which will react with the selected reactive groups on the precursoroligomer to provide attachment of the crosslinker group orwater-dispersing group to the polyurethane oligomer(s) via covalentbonding.

To prepare an autoxidisably crosslinkable polyurethane oligomer(s)preferably an isocyanate-reactive organic compound(s) bearing anunsaturated fatty acid group(s) as crosslinker group(s) may be used inthe polyurethane oligomer(s) synthesis. Such isocyanate-reactive organiccompounds bearing fatty acid groups may be obtained by using techniquesknown in the art, e.g. from the reaction of a suitable fatty acid with ahydroxyl donor (preferably an alcohol or polyol) or amine donor toprovide a compound bearing fatty acid groups) and at least one(preferably at least two) isocyanate-reactive groups.

Suitable polyisocyanates include aliphatic, cycloaliphatic, araliphaticand/or aromatic polyisocyanates. Examples of suitable polyisocyanatesinclude ethylene diisocyanate, 1,6-hexamethylene diisocyanate,isophorone diisocyanate, cyclohexane-1,4-diisocyanate,4,4′-dicyclohexylmethane diisocyanate, p-xylylene diisocyanate,α,α′-tetramethylxylene diisocyanate, 1,4-phenylene diisocyanate,2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4′-diphenylmethanediisocyanate, polymethylene polyphenyl polyisocyanates,2,4′-diphenylmethane diisocyanate, 3(4)-isocyanatomethyl-1-methylcyclohexyl isocyanate and 1,5-naphthylene diisocyanate. Mixtures ofpolyisocyanates can be used and also polyisocyanates which have beenmodified by the introduction of urethane, allophanate, urea, biuret,carbodiimide, uretonimine, urethdione or isocyanurate residues.

Other isocyanate-reactive organic compounds bearing neither crosslinkergroups (such as unsaturated fatty acid groups) nor hydrophilicwater-dispersing groups which may be used in the preparation ofpolyurethane oligomer(s) or polyurethane prepolymers preferably containat least one (preferably at least two) isocyanate-reactive groups, andare more preferably organic polyols. The organic polyols particularlyinclude diols and triols and mixtures thereof but higher functionalitypolyols may be used, for example as minor components in admixture withdiols. The polyols may be members of any of the chemical classes ofpolyols used or proposed to be used in polyurethane formulations. Inparticular the polyols may be polyesters, polyesteramides, polyethers,polythioethers, polycarbonates, polyacetals, polyolefins orpolysiloxanes. Preferred polyol molecular weights are from 250 to 6000,more preferably from 500 to 3000. Low molecular weight organic compoundscontaining at least one (preferably at least two) isocyanate-reactivegroups and having a weight average molecular weight up to 500,preferably in the range of 40 to 250 can also be used. Examples includeethyleneglycol, neopentyl glycol, 1-propanol, and1,4-cyclohexyldimethanol.

Hydrophilic water-dispersing groups are optionally incorporated into thepolyurethane oligomer(s) by including an isocyanate-reactive and/orisocyanate functional compound(s) bearing a non-ionic and/or ionichydrophilic water-dispersing group(s) (as described above) (or groupwhich may be subsequently easily converted to such a water-dispersinggroup, e.g. by neutralisation, such a group still being termed a waterdispersing group for the purposes of this invention) as a reactant inthe preparation of the polyurethane oligomer or prepolymer. Examples ofsuch compounds include carboxyl group containing diols and triols, forexample dihydroxy alkanoic acids such as 2,2-dimethylolpropionic acid or2,2-dimethylolbutanoic acid. Examples of preferred compounds bearingnon-ionic hydrophilic water-dispersing groups include methoxypolyethylene glycol (MPEG) with molecular weights of for example 350,550, 750, 1000 and 2000, as described in EP 0317258.

The polyurethane oligomer(s) preferably has an acid value in the rangeof from 0 to 50 mg KOH/g, more preferably in the range of from 0 to 40mg KOH/g and most preferably in the range of from 10 to 35 mg KOH/g.

When an isocyanate-terminated polyurethane prepolymer is prepared, it isconventionally formed by reacting a stoichiometric excess of the organicpolyisocyanate with the isocyanate-reactive compounds undersubstantially anhydrous conditions at a temperature between about 30° C.and about 130° C. until reaction between the isocyanate groups and theisocyanate-reactive groups is substantially complete; the reactants forthe prepolymer are generally used in proportions corresponding to aratio of isocyanate groups to isocyanate-reactive groups of from about1.1:1 to about 6:1, preferably from about 1.5:1 to 3:1.

When a hydroxyl-terminated polyurethane oligomer(s) is prepared directly(i.e. not proceeding through the prepolymer/chain-extension route), itis conventionally formed by reacting a stoichiometric excess of theisocyanate-reactive compounds with the organic polyisocyanate undersubstantially anhydrous conditions at a temperature between about 30° C.and about 130° C. until reaction between the isocyanate groups and theisocyanate-reactive groups is substantially complete; the reactants forthe oligomer are generally used in proportions corresponding to a ratioof isocyanate groups to isocyanate-reactive groups of from about 0.4:1to about 0.99:1, preferably from about 0.55:1 to 0.95:1.

If desired, catalysts such as dibutyltin dilaurate and stannous octoate,zirconium or titanium based catalysts may be used to assist polyurethaneoligomer(s) formation. An organic solvent may optionally be added beforeor after prepolymer or final oligomer formation to control theviscosity. Examples of solvents include water-miscible solvents such asN-methylpyrrolidone, dimethyl acetamide, glycol ethers such asbutyldiglycol, methyl ethyl ketone and alkyl ethers of glycol acetatesor mixtures thereof. Optionally no organic solvents are added.

The polyurethane oligomer(s) may be dispersed in water using techniqueswell known in the art. Preferably, the polyurethane oligomer(s) is addedto the water with agitation or, alternatively, water may be stirred intothe polyurethane oligomer(s).

An aqueous polyurethane oligomer(s) dispersion may also be prepared,when the urethane synthesis has employed the prepolymer/chain extensionroute, by dispersing the isocyanate-terminated polyurethane prepolymer(optionally carried in an organic solvent medium) in an aqueous medium(using surfactants, or more preferably by utilising theself-dispersability of the prepolymer if dispersing groups in asufficient amount are present therein, although surfactants may still beemployed if desired) and chain extending the prepolymer with activehydrogen-containing chain extender in the aqueous phase.

Active hydrogen-containing chain extenders which may be reacted with theisocyanate-terminated polyurethane prepolymer include amino-alcohols,primary or secondary diamines or polyamines, hydrazine, and substitutedhydrazines.

Examples of such chain extenders useful herein include alkylene diaminessuch as ethylene diamine and cyclic amines such as isophorone diamine.Also materials such as hydrazine, azines such as acetone azine,substituted hydrazines such as, for example, dimethyl hydrazine,1,6-hexamethylene-bis-hydrazine, carbodihydrazine, hydrazides ofdicarboxylic acids and sulphonic acids such as adipic acid mono- ordihydrazide, oxalic acid dihydrazide, isophthalic acid dihydrazide,hydrazides made by reacting lactones with hydrazine such asgammahydroxylbutyric hydrazide, bis-semi-carbazide, and bis-hydrazidecarbonic esters of glycols may be useful. Water itself may be effectiveas an indirect chain extender.

Where the chain extender is other than water, for example a polyamine orhydrazine, it may be added to the aqueous dispersion of theisocyanate-terminated polyurethane prepolymer or, alternatively, it mayalready be present in the aqueous medium when the isocyanate-terminatedpolyurethane prepolymer is dispersed therein. The isocyanate-terminatedpolyurethane prepolymer may also be chain extended to form thepolyurethane oligomer(s) while dissolved in organic solvent (usuallyacetone) followed by the addition of water to the solution until waterbecomes the continuous phase and the subsequent removal of the solventby distillation to form an aqueous dispersion.

Optionally a combination of chain extender(s) and chain terminator(s)may be used. Examples of chain terminators are mono-functionalisocyanate-reactive compounds such as mono-alcohols, mono-amines,mono-hydrazines and mono-mercaptanes. The ratio of chain extender tochain terminator compounds is preferably in the range of from 95:5 to5:95, more preferably 50:50 to 10:90 and most preferably 35:65 to 20:80.

The chain extension and/or chain termination can be conducted atelevated, reduced or ambient temperatures. Convenient temperatures arefrom about 5° C. to 95° C. or, more preferably, from about 10° C. to 60°C.

The total amount of chain extender and chain terminating materialsemployed (apart from water) should be such that the ratio of activehydrogens in the chain extender(s) to isocyanate groups in thepolyurethane prepolymer preferably is in the range from 0.1:1 to 2.0:1more preferably 0.80:1 to 1.7:1.

Any other known methods for preparing polyurethane dispersions such as aketamine/ketazine process or a hot process as described in “Progress inOrganic Coatings”, D. Dietrich, 9, 1981, p 281) may also be utilised.

Surfactants and or high shear can be utilised in order to assist in thedispersion of the polyurethane oligomer(s) in water (even if it isself-dispersible). Suitable surfactants include but are not limited toconventional anionic, cationic and/or non-ionic surfactants such as Na,K and NH₄ salts of dialkylsulphosuccinates, Na, K and NH₄ salts ofsulphated oils, Na, K and NH₄ salts of alkyl sulphonic acids, Na, K andNH₄ alkyl sulphates, alkali metal salts of sulphonic acids; fattyalcohols, ethoxylated fatty acids and/or fatty amides, and Na, K and NH₄salts of fatty acids such as Na stearate and Na oleate. Other anionicsurfactants include alkyl or (alk)aryl groups linked to sulphonic acidgroups, sulphuric acid half ester groups (linked in turn to polyglycolether groups), phosphonic acid groups, phosphoric acid analogues andphosphates or carboxylic acid groups. Cationic surfactants include alkylor (alk)aryl groups linked to quaternary ammonium salt groups. Non-ionicsurfactants include polyglycol ether compounds and polyethylene oxidecompounds. The amount of surfactant used is preferably 0 to 15% byweight, more preferably 0 to 8% by weight, still more preferably 0 to 5%by weight, especially 0.1 to 3% by weight, and most especially 0.3 to 2%by weight based on the weight of the crosslinkable polyurethaneoligomer(s).

The polyurethane oligomer(s) has at least one glass transitiontemperature (Tg) as measured by modulated differential scanningcalorimetry (DSC), preferably being in the range of from −100 to 250°C., more preferably −80 to 150° C. and most preferably −70 to 130° C.and especially −70 to 30° C.

The aqueous composition of the invention may optionally but preferablyinclude a polymer(s) dispersed therein which is not a crosslinkablepolyurethane oligomer (or a non-polyurethane oligomer whethercrosslinkable or non-crosslinkable) and has a Mw≧90,000 Daltons, hereintermed a “dispersed polymer” for convenience. Preferably the weightaverage molecular weight of the dispersed polymer(s) Mw in the aqueouspolymer dispersion is in the range of from 90,000 to 6,000,000, morepreferably in the range of from 150,000 to 2,000,000, and especially inthe range of from 250,000 to 1,500,000 Daltons. If the dispersedpolymer(s) is fully precrosslinked its Mw will be infinite. Also, insome cases, the synthesis to form the crosslinkable polyurethaneoligomer yields, in addition to the low molecular weight oligomer, anamount of very high molecular material. For the purposes of thisinvention, such material, produced in-situ, is to be considered as adispersed polymer.

The Mw of the dispersed polymer(s) may be <90,000 Daltons, with theproviso that the solution viscosity of the dispersed polymer(s) is atleast 150 Pa·s as determined from a 80% by weight solids solution of thedispersed polymer(s) in at least one of the one or other of two solventsselected from the group consisting of N-methylpyrrolidone, n-butylglycoland mixtures thereof using a shear rate of 90±5 s⁻¹ and at 50±2° C.

Preferably the solution viscosity (if measurable) of the dispersedpolymer(s) when used in the aqueous composition of the invention is ≧250Pa·s, more preferably ≧500 Pa·s, and especially ≧1000 Pa·s as determinedfrom a 80% by weight solids solution of the dispersed polymer(s) in atleast one of the solvents, from the group consisting ofN-methylpyrrolidone, n-butylglycol and mixtures thereof using a shearrate of 90±5 s⁻¹ and at 50±2° C.

The solution viscosity of the dispersed polymer(s) may not be measurableif for example the weight average molecular weight is so high so as torender the dispersed polymer(s) insoluble in organic solvent(s) or ifthe dispersed polymer(s) is fully or partially crosslinked, againrendering it insoluble.

The dispersed polymer(s) may be film forming or non-film forming atambient temperature; preferably the dispersed polymer(s) is non-filmforming at ambient temperature (ambient temperature as used herein isdefined as 23±2° C.). Preferably the aqueous composition of theinvention does include such a dispersed polymer(s).

The crosslinkable polyurethane oligomer(s) can thus be (and preferablyis) combined with a dispersed polymer(s) to further improve theprovision of a binder system for providing an aqueous composition withthe desired balance of long open/wet edge time and reduced tack freetime.

The presence of the crosslinkable polyurethane oligomer(s) (as discussedabove) provides the defined long open time and wet edge time, whilst thepresence of the dispersed polymer(s) (e.g. in the form of a polymerlatex) appears to assist in reducing the drying time of the composition,even though its presence may not always be essential to achieve thebroadest scope of defined requirements in this respect.

Accordingly in a further, and preferred, embodiment of the presentinvention there is provided an aqueous coating composition as definedherein additionally comprising a dispersed polymer(s).

The dispersed polymer(s) may for example be the product of an aqueousemulsion polymerisation or a preformed polymer dispersed in water.

Preferably the dispersed polymer(s) has a measured Tg (using DSC) whichis preferably in the range of from −50 to 300° C., and more preferablyin the range of from 25 to 200° C. and especially in the range of from35 to 125° C. If the dispersed polymer(s) is a vinyl polymer, the vinylpolymer may be a sequential polymer, i.e. the vinyl polymer will havemore than one Tg. Especially preferred is a vinyl polymer with 10 to 50wt. % of a soft part with a Tg in the range of from −30 to 20° C. and 50to 90 wt. % of a hard part of with a Tg in the range of from 60 to 110°C. This combination provides an additional advantage of improved blockresistance of the resultant coating, especially when co-solvent levelsof 0 to 15 wt. %, more preferably 0 to 5 wt. % and most preferably 0 to3 wt. %. of the aqueous composition are used. Blocking is the well-knownphenomenon of coated substrates which are in contact tending tounacceptably adhere to each other, for examples doors and windows intheir respective frames, particularly when under pressure, as forexample in stacked panels.

Preferably the dispersed polymer(s) has an average particle size in therange of from 25 to 1000 nm, more preferably 60 to 700 nm, morepreferably 100 to 600 nm and especially in the range of from 150 to 500nm. The dispersed polymer(s) may also have a polymodal particle sizedistribution.

The dispersed polymer(s) may for example be a vinyl polymer,polyurethane (in some cases, an in-situ formed very high molecularpolyurethane resulting from the urethane synthesis as discussed above),polyester, polyether, polyamide, polyepoxide, or a mixture thereof. Thedispersed polymer(s) may also be a hybrid of two or more differentpolymer types such as urethane-acrylic polymers (as described in forexample U.S. Pat. No. 5,137,961), epoxy-acrylic polymers andpolyester-acrylic polymers. The dispersed polymer(s) may also be anorganic-inorganic hybrid, for example silica particles grafted with avinyl polymer(s). Preferably the dispersed polymer(s) is a vinylpolymer. Blends of dispersed polymers may of course also be used.

The dispersed polymer(s) may optionally contain acid groups. Thepreferred acid value of the dispersed polymer(s) depends on the type andmolecular weight of crosslinkable polyurethane oligomer and (if present)the type of cosolvent used. If the crosslinkable polyurethane oligomeris hydrophilic, the cosolvent (if used) is preferably also of ahydrophilic nature and a low acid value of the dispersed polymer(s) ispreferred (preferably below 60, more preferably below 40, still morepreferably below 30, especially below 24, more especially below 19 andmost especially below 15 mg KOH/g). If however a hydrophobiccrosslinkable polyurethane oligomer is used, for instance based on (atleast partly) unsaturated fatty acid and without dispersing groups, theco-solvent is preferentially of a hydrophobic nature (if at all present)and therefore much higher acid values (up to an acid value of 160, morepreferably up to an acid value of 125, most preferably up to an acidvalue of 100 mg KOH/g) of the dispersed polymer(s) may be tolerated togive the desired properties.

In a special embodiment, ≦15 wt. % of a co-solvent (based on totalbinder polymer solids) where the binder includes the crosslinkableoligomer(s), non-crosslinkable oligomer(s) and any dispersed polymer(s)is used, where the dispersed polymer(s) has an acid value below 20 mgKOH/g and the crosslinkable polyurethane oligomer(s) is present in anamount (based on total binder polymer solids) of 35 to 65 wt. %, thecrosslinkable polyurethane oligomer(s) comprising 45 to 70 wt. % offatty acid groups.

The dispersed polymer(s) may optionally contain hydroxyl groups. If thedispersed polymer(s) is a vinyl polymer comprising polymerised(meth)acrylic monomers then preferably the hydroxyl group content in thevinyl polymer is preferably below 1.0 wt. %, more preferably below 0.5wt. % and most preferably below 0.2 wt. % based on the weight of thevinyl polymer.

The dispersed polymer(s) may optionally contain amide groups (suchgroups being e.g. obtainable from amide functional monomers such as(meth)acrylamide). If the dispersed polymer(s) is a vinyl polymercomprising polymerised (meth)acrylamide monomers, then preferably theamide group content in the vinyl polymer is below 3.0 wt. %, morepreferably below 1.5 wt. % and most preferably below 0.6 wt. % based onthe weight of the vinyl polymer.

The dispersed polymer(s) may optionally contain wet-adhesion promotinggroups such as acetoacetoxy groups, (optionally substituted) amine orurea groups, for example cyclic ureido groups, imidazole groups,pyridine groups, hydrazide or semicarbazide groups.

The dispersed polymer(s) may optionally contain crosslinker groups whichallow independent crosslinking of the dispersed polymer(s) and/or allowparticipation in the crosslinking reaction of the crosslinkablepolyurethane oligomer(s), thus speeding up the drying rate and improvingthe properties of the final coating (e.g. chemical resistance andscratch resistance). Examples of such crosslinker groups include groupswhich can take part in the autoxidation and groups which will effectcrosslinking other than by autoxidation, for example by Schiff base andsilane condensation reactions as discussed above for polyurethaneoligomer(s).

In a preferred embodiment the dispersed polymer(s) contains crosslinkergroups which can participate in the preferred autoxidative crosslinkingreactions of an autoxidisably crosslinkable polyurethane oligomer(s).

In a preferred embodiment the dispersed polymer(s) may be fully orpartially pre-crosslinked (i.e. fully or partially crosslinked whilepresent in the invention aqueous coating composition and prior toapplying a coating). If the dispersed polymer(s) is a vinyl polymerpre-crosslinking may be achieved by using polyunsaturated monomersduring the vinyl polymer synthesis such as allyl methacrylate, diallylphthalate, tripropylene glycol di(meth)acrylate, 1,4-butanedioldiacrylate and trimethylol propane triacrylate. Allyl methacrylate ismost preferred. Alternatively very low levels of initiator may be used,leading to chain-transfer to the vinyl polymer and hence to grafting andhigh Mw. Other ways to generate pre-crosslinking in a vinyl polymer isto include the use of monomer(s) bearing groups which may react witheach other during synthesis to effect pre-crosslinking for exampleglycidylmethacrylate and acrylic acid.

Vinyl polymers are derived from free radically polymerisableolefinically unsaturated monomers (herein used as the definition ofvinyl monomers) and can contain polymerised units of a wide range ofsuch vinyl monomers, especially those commonly used to make binders forthe coatings industry.

Examples of vinyl monomers which may be used to form vinyl polymer(s)include but are not limited to 1,3-butadiene, isoprene, styrene,α-methyl styrene, divinyl benzene, acrylonitrile, methacrylonitrile,vinyl halides such as vinyl chloride, vinylidene halides such asvinylidene chloride, vinyl esters such as vinyl acetate, vinylpropionate, vinyl laurate, and vinyl esters of versatic acid such asVeoVa 9 and VeoVa 10 (VeoVa is a trademark of Shell), heterocyclic vinylcompounds, alkyl esters of mono-olefinically unsaturated dicarboxylicacids (such as di-n-butyl maleate and di-n-butyl fumarate) and, inparticular, esters of acrylic acid and methacrylic acid of formulaCH₂═CR¹—COOR²wherein R¹ is H or methyl and R² is optionally substituted alkyl orcycloalkyl of 1 to 20 carbon atoms (more preferably 1 to 8 carbon atoms)examples of which are methyl acrylate, methyl methacrylate, ethylacrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate,2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, isopropyl acrylate,isopropyl methacrylate, n-propyl acrylate, n-propyl methacrylate, andhydroxyalkyl (meth)acrylates such as hydroxyethyl acrylate, hydroxyethylmethacrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate,4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate and their modifiedanalogues like Tone M-100 (Tone is a trademark of Union CarbideCorporation).

Olefinically unsaturated monocarboxylic, sulphonic and/or dicarboxylicacids, such as acrylic acid, methacrylic acid, β-carboxy ethyl acrylate,fumaric acid and itaconic acid, and monomers such as (meth)acrylamideand methoxy polyethyleneoxide (meth)acrylate may also be used.

The vinyl monomer may optionally contain functional groups to contributeto the crosslinking of the vinyl polymer(s) in the coating. Examples ofsuch groups include maleic, epoxy, fumaric, acetoacetoxy, β-diketone,unsaturated fatty acid, acryloyl, methacrylol, styrenic, (meth)allylgroups, mercapto groups, keto or aldehyde groups (such asmethylvinylketone, diacetoneacrylamide and (meth)acroleine).

Particularly preferred are vinyl polymer(s) made from a monomer systemcomprising at least 40 wt. % of one or more monomers of the formulaCH₂═CR¹COOR² defined above. Such preferred vinyl polymer(s) are definedherein as acrylic polymer(s). More preferably, the monomer systemcontains at least 50 wt. % of such monomers, and particularly at least60 wt. %. The other monomers in such acrylic polymer(s) (if used) mayinclude one or more of the other vinyl monomers mentioned above, and/ormay include ones different to such other monomers. Particularlypreferred monomers include butyl acrylate (all isomers), butylmethacrylate (all isomers), methyl methacrylate, ethyl hexylmethacrylate, esters of (meth)acrylic acid, acrylonitrile, vinyl acetateand styrene.

If the dispersed polymer(s) is a vinyl polymer, the dispersed vinylpolymer may in some embodiments comprise at least 15 wt. %, morepreferably at least 40 wt. % and most preferably at least 60 wt. % ofpolymerised vinyl acetate. If the dispersed vinyl polymer comprises atleast 50 wt. % of polymerised vinylacetate then preferably the dispersedvinyl polymer also comprises 1049 wt. % of either n-butylacrylate or abranched vinylester, for example Veova 10.

In a preferred embodiment the dispersed vinyl polymer comprises:

-   -   I. 15 to 60 wt. % of styrene and/or α-methylstyrene;    -   II. 15 to 80 wt. % of one or more of methyl methacrylate, ethyl        methacrylate, cyclohexyl (meth)acrylate and n-butyl        methacrylate;    -   III. 0 to 5 wt. %, more preferably 0 to 3.5 wt. %, of vinyl        monomer(s) containing a carboxylic acid group(s);    -   IV. 0 to 10 wt. %, more preferably 0 to 5 wt. % of vinyl        monomer(s) containing a non-ionic water-dispersing group(s);    -   V. 5 to 40 wt. % of vinyl monomer(s) other than as in I to IV,        VI and VII;    -   VI. 0 to 5 wt. % of vinyl monomer(s) containing wet adhesion        promoter or crosslinker groups (excluding any within the scope        of III and VII); and    -   VII. 0 to 8 wt. %, more preferably 0 to 4 wt. %, and most        preferably 0.5 to 3 wt. % of a polyethylenically unsaturated        vinyl monomer,        wherein I)+II) add up to at least 50 wt. % and        I+II+III+IV+V+VI+VII add up to 100%.

The dispersed polymer(s) can be prepared by any known technique.Preparation techniques particularly include either dispersing apre-formed polymer or polymer solution in water or if the dispersedpolymer(s) is a vinyl polymer directly synthesising the vinyl polymer inwater (for example by emulsion polymerisation, micro-suspensionpolymerisation or mini emulsion polymerisation). Methods for preparingaqueous dispersed polymer(s) are reviewed in the Journal of CoatingTechnology volume 66, number 839, pages 89-105 (1995) and these methodsare included herein by reference. Preferably dispersed vinyl polymer(s)are prepared by the emulsion polymerisation of free radicallypolymerisable olefinically unsaturated monomers (Emulsion Polymerisationand Emulsion Polymers, P. Lovell, M. S. El-Aasser, John Wiley, 1997).Any published variant of the emulsion polymerisation process may beutilised to prepare the dispersed polymer(s), including the use ofseeded emulsion polymerisation techniques to control particle size andparticle size distribution, especially when working in the particle sizerange 300-700 nm when the seeded technique is useful for giving goodparticle size control. Other useful techniques are the so calledsequential polymerisation technique and the power feed technique(chapter 23 in “Emulsion Polymers and Emulsion Polymerisation” D RBasset and A E Hamielec, ACS Symposium Series No 165,1981).

Preferably the dispersed polymer(s) is colloid stable and it is alsodesirable that colloid stability is maintained for as long as possibleinto the drying process since early loss of colloid stability can bringa premature end to open time. Since the final coating composition mayoften contain co-solvents and dissolved ionic species (e.g. from pigmentdissolution and from the presence of neutralising agents), it isdesirable that the colloid stability of the dispersed polymer(s) isadequate to withstand any destabilising influences of these components.Colloid stability may be achieved by the addition of conventionalnon-ionic surfactants, optionally with the addition of anionicsurfactants at any stage during the preparation of the aqueouscomposition of the invention. Strongly adsorbing surfactants capable ofproviding steric stability are preferred. Higher levels of colloidstability may be obtained by chemically binding or partially bindinghydrophilic stabilising groups such as polyethylene oxide groups to thesurface of dispersed polymer(s) particles. Suitable surfactants andstabilising groups are described in “Non Ionic Surfactants-PhysicalChemistry” (M J Schick, M Dekker Inc. 1987) and “Polymer Colloids”(Buscall, Corner & Stageman, Elsevier Applied Science Publishers 1985).

Chemical binding (grafting) of hydrophilic stabilising groups ontodispersed polymer(s) particles can be achieved by the use of acomonomer, polymerisation initiator and/or chain transfer agent bearingthe stabilising group, for example methoxy(polyethylene oxide)₃₀methacrylate may be introduced as a comonomer into an emulsionpolymerisation to give rise to stabilised dispersed polymer particleswith bound polyethylene oxide groups on the particle surface. Anothermethod of producing a strongly sterically stabilised dispersedpolymer(s) is to introduce cellulosic derivatives (e.g. hydroxy ethylcellulose) during an emulsion polymerisation (see for example DH Craig,Journal of Coatings Technology 61, no. 779, 48, 1989). Hydrophilicstabilising groups may also be introduced into a preformed polymerbefore it is subsequently dispersed in water, as described in EP 0317258where polyethylene oxide groups are reacted into a polyurethane polymerwhich is subsequently dispersed in water and then chain extended.

The combination of crosslinkable polyurethane oligomer(s) (and othercrosslinkable or non-crosslinkable oligomers, if used) and dispersedpolymer(s) is most conveniently prepared by physically blending thecorresponding aqueous dispersions. However other methods of preparingthe combination can sometimes be utilised. One such method is to preparethe crosslinkable polyurethane oligomer(s) in organic solvent solutionas previously discussed, and to disperse this solution directly into anaqueous dispersed polymer(s). Alternatively the organic solvent can beremoved from the crosslinkable polyurethane oligomer(s) solution, andthe polyurethane oligomer(s) directly dispersed into an aqueousdispersed polymer(s). The dispersed polymer can also be added to anorganic solvent solution of the polyurethane oligomer(s). Another methodis to introduce the crosslinkable polyurethane oligomer(s) into anaqueous free radical polymerisation reaction which produces thedispersed polymer(s). Such an introduction of polyurethane oligomer(s)may be at the commencement of the aqueous free radical polymerisationand/or during the aqueous free radical polymerisation. (Also, asmentioned previously, a dispersed polymer can sometimes be formedin-situ from the synthesis of a polyurethane oligomer as a very highmolecular weight polymer fraction resulting from the urethanesynthesis).

The crosslinkable polyurethane oligomer(s) may also be diluted withreactive diluent (for example vinyl monomers) at any stage of itspreparation and then dispersed in water optionally containing adispersed polymer(s), followed by polymerisation of the reactive diluentin the presence of the polyurethane oligomer(s) and the optionaldispersed polymer(s). Optionally, depending on the nature of thereactive diluent, no further polymerisation of the reactive diluentprior to use in a coating may be required.

Alternatively the crosslinkable polyurethane oligomer(s) and dispersedpolymer(s) may be combined by preparing a redispersible dry powder formof the dispersed polymer(s), and then dispersing the redispersible drypowder directly into an aqueous dispersion of the crosslinkablepolyurethane oligomer(s). Methods for preparing redispersible drypowders from polymer emulsions are described for example in U.S. Pat.No. 5,962,554, DE 3323804 and EP 0398576.

In an embodiment of the invention the crosslinkable polyurethaneoligomer(s) and the dispersed polymer(s) are compatible in the dryingaqueous composition. Preferably the crosslinkable polyurethaneoligomer(s) and the dispersed polymer(s) give clear films upon filmformation after coating of the aqueous composition onto a substrate.

Preferably the ratios by weight of solid material of crosslinkablepolyurethane oligomer(s) (and other crosslinkable or non-crosslinkableoligomers, if used) to dispersed polymer(s) are in the range of from100:0 to 10:90, more preferably in the range of from 90:10 to 20:80,still more preferably in the range of from 75:25 to 25:75, andespecially in the range of from 65:35 to 35:65.

The aqueous coating compositions of the invention are particularlyuseful when in the form of final coating formulations (i.e. compositionintended for application to a substrate without any further treatment oradditions thereto) such as protective or decorative coating compositions(for example paint, lacquer or varnish) wherein an initially preparedcomposition may be further diluted with water and/or organic solventsand/or combined with further ingredients, or may be in more concentratedform by optional evaporation of water and/or organic components of theliquid medium of an initially prepared composition. The inventioncomposition can contain a co-solvent or a mixture of co-solvents. Morepreferably the invention composition can contain co-solvent or a mixtureof co-solvents in a concentration ≦18%, more preferably ≦10%, especially≦5%, most preferably ≦3% and most especially 0% by weight based on theinvention composition.

Preferably the evaporation rate of the co-solvent is ≦0.6, morepreferably ≦0.15, most preferably ≦0.08 and especially ≦0.035. Valuesfor evaporation rates were published by Texaco Chemical Company in abulletin Solvent Data: Solvent Properties (1990). (The values given arerelative to the evaporation rate (ER) is defined as 1.00). Determinationof evaporation rates of solvents that are not listed the Texaco bulletinis as described in ASTM D3539.

In a special embodiment, the amount of co-solvent(s) used in theinvention composition is preferably linked to the Mw of thecrosslinkable polyurethane oligomer(s) in the composition. Forcrosslinkable polyurethane oligomer(s) with Mw in the range 1,000 to40,000 Daltons, the amount of co-solvent is preferably 0 to 15 wt. %based on the weight of the composition, more preferably 0 to 10 wt. %.For crosslinkable polyurethane oligomer(s) with Mw in the range >40,000to 80,000 Daltons, the corresponding figures for the preferred amount ofco-solvent are 0 to 25 wt. %, more preferably 5 to 20 wt. %.

Furthermore, there is also a preferred relationship between the amountof co-solvent used and the amount of binder polymer solids (oligomerplus dispersed polymer), viz the amount of co-solvent is preferably ≦50wt % based on the weight of binder polymer solids in the composition,more preferably ≦35 wt %, more preferably ≦20 wt %, more preferably ≦10wt %, and especially preferably 0 wt %.

An advantage of the present invention is that (if used) co-solvent can;if as is often required for environmental and safety reasons, be presentat a very low concentrations because of the plasticising nature of thecrosslinkable polyurethane oligomer(s). Preferably the co-solvent towater ratio is below 1.0, more preferably below 0.5, most preferablybelow 0.3 and especially below 0.15. The co-solvent(s) can all be addedat the final formulation step. Alternatively some or all of theco-solvent in the final formulation can be the co-solvent utilised inthe preparation of the crosslinkable polyurethane oligomer. An importantconsideration when choosing a co-solvent is whether or not theco-solvent is compatible with the crosslinkable polyurethane oligomer(s)and/or the dispersed polymer(s) and the effect of any co-solventpartitioning (and the partitioning of the co-solvent in the (aqueous)oligomer phase versus the dispersed polymer particles ispreferably >1/1, more preferably >2/1 and most preferably >3/1). If theco-solvent is more compatible with the dispersed polymer it will swellthe dispersed polymer, thus increasing the overall viscosity. Preferablyany co-solvent present in the aqueous composition of the invention ismore compatible with the polyurethane oligomer(s) then with thedispersed polymer(s), so that the dispersed polymer(s) undergoes littleif any swelling by the co-solvent. The co-solvent selection is oftendetermined by experimentation and/or by the use of a solubilityparameter concept i.e. maximising the difference in the solubilityparameter of the dispersed polymer(s) and solvent leads to aminimisation of the co-solvent uptake by the dispersed polymer(s).Solubility parameters of a range of solvents and a group contributionmethod for assessing the solubility parameters of polymers are given byE A Grulke in the “Polymer Handbook” (John Wiley pages 519-559, 1989)and by D W Van Krevelen and P J Hoftyzer in “Properties of Polymers.Correlations With Chemical Structure” (Elsevier, New York, 1972 chapters6 and 8). Co-solvent uptake of the dispersed polymer(s) may also bedecreased by increasing its Tg so that the dispersed polymer(s) is inthe glassy region at ambient temperature, or by pre-crosslinking thedispersed polymer(s) as described above. Other ways of introducingpre-cross linking into dispersed polymer(s) are known in the art, forexample U.S. Pat. No. 5,169,895 describes the preparation ofpre-crosslinked polyurethane aqueous dispersions by the use oftri-functional isocyanates in the synthesis.

A known problem with many autoxidisable coating compositions is that theresultant coatings have a tendency to yellow, in particular where theautoxidisable groups are derived from polyunsaturated fatty acids, suchas for example tung oil fatty acid, linolenic acid, eleostearic acid,arachidonic acid, clupanadonic acid, and fatty acids obtainable fromdehydrated castor oil. This may be unacceptable depending on the desiredcolour of the resultant coating. Preferably the aqueous composition hasa starting yellowness value of less than 10, more preferably less than 7and most preferably less than 4, measured as described herein.Preferably the aqueous composition has an increase in yellowing indarkness of less than 7, more preferably less than 5, most preferablyless than 3 and preferably the aqueous composition has an increase inyellowing in daylight of preferably less than 4, preferably less than 3and more most preferably less than 2 as measured by the test methoddescribed herein. Furthermore, the absolute yellowness (i.e. yellownessat start plus yellowness due to ageing) of the aqueous composition ispreferably less than 12, more preferably less than 10, still morepreferably less than 8, and most preferably less than 6.

In a further embodiment of the present invention there is provides anaqueous coating composition as defined herein comprising:

i) 3 to 26% of a crosslinkable oligomer(s) by weight of the compositionof which at least 52 wt % is a crosslinkable water-dispersiblepolyurethane oligomer(s);

ii) 0 to 6.5% of a non-crosslinkable oligomer(s) by weight of thecomposition;

iii) 10 to 56% of dispersed polymer(s) by weight of the composition;

iv) 0 to 15% of co-solvent by weight of the composition;

v) 5 to 65% of water by weight of the composition;

where i)+ii)+iii)+iv)+v)=100%.

In another embodiment of the present invention there is provided anaqueous coating composition as defined herein comprising:

i) 15 to 40% of a crosslinkable oligomer(s) by weight of crosslinkableoligomer(s), non-crosslinkable oligomer(s) and dispersed polymer(s) ofwhich at least 52 wt % is a crosslinkable water-dispersible polyurethaneoligomer(s);

ii) 0 to 10% of a non-crosslinkable oligomer(s) by weight ofcrosslinkable oligomer(s), non-crosslinkable oligomer(s) and dispersedpolymer(s);

iii) 50 to 85% of dispersed polymer(s) by weight of crosslinkableoligomer(s), non-crosslinkable oligomer(s) and dispersed polymer(s);

where i)+ii)+iii)=100%.

The aqueous coating composition of the invention may be applied to avariety of substrates including wood, board, metals, stone, concrete,glass, cloth, leather, paper, plastics, foam and the like, by anyconventional method including brushing, dipping, flow coating, spraying,and the like. They are, however, particularly useful for providingcoatings on wood and board substrates. The aqueous carrier medium isremoved by natural drying or accelerated drying (by applying heat) toform a coating.

Accordingly, in a further embodiment of the invention there is provideda coating obtainable from an aqueous coating composition of the presentinvention. The aqueous coating composition of the invention may containother conventional ingredients, some of which have been mentioned above;examples include pigments, dyes, emulsifiers, surfactants, plasticisers,thickeners, heat stabilisers, levelling agents, anti-cratering agents,fillers, sedimentation inhibitors, UV absorbers, antioxidants,dispersants, flow agents, adhesion promoters, defoamers, co-solvents,wetting agents and the like introduced at any stage of the productionprocess or subsequently. It is possible to include an amount of antimonyoxide in the dispersions to enhance the fire retardant properties.Optionally external crosslinking agent(s) may be added to the aqueouscomposition of the invention to aid crosslinking during and afterdrying. Examples of reactive functional groups which may be utilised forexternal crosslinking agent(s) include but are not limited to hydroxylfunctional groups reacting with isocyanate (optionally blocked),melamine, or glycouril functional groups; keto, aldehyde and/oracetoacetoxy carbonyl functional groups reacting with amine or hydrazinefunctional groups; carboxyl functional groups reacting with aziridine,epoxy or carbodiimide functional groups; silane functional groupsreacting with silane functional groups; epoxy functional groups reactingwith amine or mercaptane groups as well as carboxyl functional groupsundergoing metal ion (such as zinc) crosslinking.

In particular, the aqueous coating compositions of the invention, ifautoxidisable, advantageously include a drier salt(s). Drier salts arewell known to the art for further improving curing in unsaturatedfilm-forming substances. Generally speaking, drier salts are metallicsoaps, that is salts of metals and long chain carboxylic acids. It isthought that the metallic ions effect the curing action in the filmcoating and the fatty acid components confer compatibility in thecoating medium. Examples of drier metals are cobalt, manganese,zirconium, lead, neodymium, lanthanum and calcium. The level of driersalt(s) in the composition is typically that to provide an amount ofmetal(s) within the range of from 0.01 to 0.5% by weight based on theweight of autoxidisable polyurethane oligomer(s) and or autoxidisabledispersed polymer(s).

Drier salts are conventionally supplied as solutions in white spirit foruse in solvent-borne alkyd systems. They may, however, be used quitesatisfactorily in aqueous coating compositions since they can normallybe dispersed in such systems fairly easily. The drier salt(s) may beincorporated into the aqueous coating composition at any convenientstage. For example the drier salt(s) may be added prior to dispersioninto water. Drier accelerators may be added to the drier salts. Suitabledrier accelerators include 2,2′-bipyridyl and 1,10-phenanthroline.

If desired the aqueous dispersion of the invention can be used incombination with other polymer dispersions or solutions which are notaccording to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 4 illustrate the drying profile of a composition according tothe present invention [Example 9], where the equilibrium viscosity ismeasured as the solids content increases.

FIG. 1 shows the drying profile measured using a shear rate of 0.0997s⁻¹.

FIG. 2 shows the drying profile measured using a shear rate of 0.990s⁻¹.

FIG. 3 shows the drying profile measured using a shear rate of 9.97 s⁻¹.

FIG. 4 shows the drying profile measured using a shear rate of 78.6 s⁻¹.

The present invention is now illustrated by reference to the followingexamples. Unless otherwise specified, all parts, percentages and ratiosare on a weight basis. The term “working” means that the example isaccording to the invention. The term “non-working” means that it is notaccording to the invention (i.e. comparative).

Test Methods:

To test for the open time and wet edge time of the aqueous compositionsprepared as described in the examples below, the aqueous composition wasapplied using a wire rod to a test chart (18×24 cm, form 8B-display,available from Leneta Company) at a wet film thickness of 120 μm. Opentime and wet edge time tests were performed at fairly regular timeintervals according to the approximate expected final times in each case(being determined roughly from a trial run), the intervals betweenmeasurements decreasing towards the end of the run. The measurementswere carried out at relative humidity levels of 50+/−5%, temperatures of23+/−2° C. and an air flow ≦0.1 m/s.

Open Time:

The open time was determined by brushing at regular time intervals (asmentioned above) a virgin 75 cm² area of the coated chart with a brush(Monoblock no 12, pure bristles/polyester 5408-12) carrying some more ofthe composition with a brush pressure of 100-150 g during 30 seconds. Inthis time the brush was moved in one set comprising 5 times in thedirection of the width of the substrate and 5 times in the direction oflength of the substrate before visually assessing the coating. Once thecomposition carried on the brush no longer formed a homogeneous layerwith the coating on the substrate the open time was considered to beover.

Wet Edge Time:

The wet edge time was determined by brushing at regular time intervals(as mentioned above) a virgin 25 cm² edge area of the coated chart witha brush (Monoblock no 12, pure bristles/polyester 5408-12) carrying somemore of the composition with a brush pressure of 100-150 g during 30seconds. In this time the brush was moved in one set comprising 5 timesin the direction of the width of the substrate and 5 times in thedirection of length of the substrate before visually assessing thecoating. Once the composition carried on the brush no longer formed ahomogeneous layer with the coating on the substrate and/or a visible lapline could be seen the wet edge time was considered to be over.

Drying Time:

To test the dust-free, tack-free and thumb-hard drying stages of theaqueous compositions prepared in the Examples as described below, theaqueous composition was applied to a glass plate at a wet film thicknessof 80 μm. Drying time tests were performed at regular time intervals atrelative humidity levels of 50+/−5%, temperatures of 23+/−2° C. and anair flow ≦0.1 m/s.

Dust-Free Time:

The dust-free time was determined by dropping a piece of cotton wool(about 1 cm³ i.e. 0.1 g) onto the drying film from a distance of 25 cm.If the piece of cotton wool could be immediately blown from thesubstrate by a person without leaving any wool or marks in or on thefilm, the film was considered to be dust-free.

Tack-Free Time:

The tack-free time was determined by placing a piece of cotton wool(about 1 cm³, 0.1 g) on the drying film and placing a metal plate (witha diameter of 2 cm) and then a weight of 1 kg onto the piece of cottonwool (for 10 seconds). If the piece of cotton wool could be removed fromthe substrate by hand without leaving any wool or marks in or on thefilm, the film was considered to be tack-free.

Thumb-Hard Time:

The thumb-hard time was determined by placing the coated glass plate ona balance and a thumb was pressed on the substrate with a pressure of 7kg. The thumb was then rotated 90° under this pressure. If the film wasnot damaged the coating was dried down to the substrate level andconsidered to be thumb-hard.

Sandability

Sandability corresponds to the hardness of a coating at the point when acoating can be sanded properly. The composition prepared in the Examplesdescribed below was applied to a piece of wood at a wet film thicknessof 120 μm. The coating was abraded by hand with sandpaper (graindelicacy P150) at regular time intervals at relative humidity levels of50+/−5%, temperatures of 23+/−2° C. and an air flow ≦0.1 m/s. When therewas no significant clogging (or the coating started powdering) thecoating was considered to be sandable.

Water Resistance:

The compositions prepared in the examples below were cast down on Lenetatest charts Form 2C with a film thickness of 120 μm. The films weredried at room temperature for 4 hours and at 50° C. for 16 hours. Afterthey were cooled down to room temperature the films were tested forwater resistance.

A few drops of water were placed on the films and covered with a watchglass. The water was removed after 16 hours at room temperature and thedamage to the coating was assessed immediately and after four hoursrecovery. 0 Means that the coating is dissolved, 5 means that thecoating is not affected at all.

Detergent Resistance:

The compositions prepared in the examples below were cast down on Lenetatest charts Form 2C with a film thickness of 120 μm. The films weredried at room temperature for 4 hours and at 50° C. for 16 hours. Afterthey were cooled down to room temperature the films were tested fordetergent resistance.

A few drops of detergent were placed on the films and covered with awatch glass. The detergent was removed after 16 hours at roomtemperature and the damage to the coating was assessed immediately andafter four hours recovery. 0 Means that the coating is dissolved, 5means that the coating is not affected at all.

Viscosity:

All viscosity measurements were performed on a Bohlin Rheometer VOR or aTA Instruments AR1000N Rheometer, using the cup & spindle (C14), cone &plate (CP 5/30) and/or plate & plate (PP15) geometry, depending on theviscosity of the sample to be measured.

Solution Viscosity

For the solution viscosity measurements (both at 50±2° C. and at 23±2°C.), the cone & plate (CP 5/30) geometry was used and the measurementswere performed at a shear rate of 92.5 s⁻¹. If the oligomer solutionswere too low in viscosity to remain in between the cone and the plate,the Cup & Spindle C14 geometry was used and the viscosity measurementswere performed at a shear rate of 91.9 s⁻¹. For both geometries, the gapbetween the Cone and the Plate (or between the Cup and the Spindle) wasset to 0.1 mm, prior to each measurement. The solution viscosities ofthe oligomers were measured using the solvent systems and the conditionsas defined herein in the statements of invention:

-   1. The 80% solids solution: The oligomer was diluted (if necessary)    with the appropriate solvent to an 80% solids solution (in NMP, BG    or a mixture of NMP and BG at any ratio) which was homogenised by    stirring the solution for 15 minutes at 50±2° C.-   2. The 70% solids solution: The oligomer was diluted with the    appropriate solvent (or mixture of solvents) to result in a 70%    solids solution (either in NMP/water/DMEA or in BG/water/DMEA, or in    (a mixture of NMP and BG at any ratio)/water/DMEA; in both solvent    mixtures the solvents should be present in a weight ratio of 20/7/3,    respectively) which was homogenised by stirring the solution for 15    minutes at 50° C. The resulting solution was subsequently cooled    prior to the viscosity measurement at 23±2° C.

A sample of oligomer solution was placed in the appropriate measurementgeometry (Cone & Plate CP 5/30 or Cup & Spindle C14 geometry). Thesolution viscosity of the oligomer was measured at a temperature of50±2° C. for the 80% solids oligomer solution, and at ambienttemperature for the 70% solids oligomer solution. A heating/cooling unitin the measurement geometry was used to control the temperatures.

Equilibrium Viscosity

The equilibrium viscosity measurements were performed with the plate &plate geometry, with a 15 mm (P15) top-plate and a 30 mm (P30)bottom-plate. The gap between the two plates was set to 1.0 mm. Allcompositions were used at the solids level at which they were preparedand not diluted to lower solids levels.

Step 1: Three test charts were provided with coatings of identical filmthickness. The coatings were applied with a 120 μm wire rod and theactual film thickness (and its uniformity) was checked with a wet filmgauge, 20-370 μm, of Braive Instruments. The charts were dried underidentical conditions in an environment where the airflow was <0.1 m/s.

Step 2: One test chart was used to determine the solids increase intime. The weight of the film was monitored in time, starting right afterapplication of the film. After calculating the solids content at everymeasurement, a solids-time curve could be constructed and a trend linewas calculated for the solids of the film as a function of the dryingtime.

Step 3: The other two test charts were used to determine the equilibriumviscosity in time: approximately every 5 minutes a sample was scrapedfrom one test chart (in random order) and the viscosity of this samplewas measured at 23° C. at representative shear rates of 0.0997 s⁻¹,0.990 s⁻¹, 9.97 s⁻¹ and 78.6 s⁻¹. The measurements were continued for 90minutes, unless reproducible sampling from the test charts could not beperformed properly within that period of time (due to for example dryingof the film to reach the dust free time).

Step 4: The final drying curve of the coating as shown in FIGS. 1 to 4(in which the equilibrium viscosity is represented as a function of thesolids of the drying film) could be constructed from the solids-timecurve (Step 2) and the equilibrium viscosity data (Step 3). If theequilibrium viscosity at a shear rate of 9.97 s⁻¹ is lower than theequilibrium viscosity at a shear rate of 0.99 s⁻¹, which in turn islower than the equilibrium viscosity at a shear rate of 0.0997 s⁻¹, thecomposition may be regarded as shear thinning. If this was the case thenthe equilibrium viscosity at 79.6 s⁻¹ was not always measured as itwould inherently always be lower than the equilibrium viscosity at ashear rate of 9.97 s⁻¹.

Measurement of Film Yellowing:

The yellowness of a fresh coating and the increased yellowing of acoating exposed to daylight or darkness for a specified time period wasdetermined using a Tristimulus Colorimeter consisting of a data-station,a micro-colour meter, a calibration plate with a defined x, y and zvalue and a printer. The equipment was calibrated to the defined valuesof the calibration plate and then colour co-ordinates L, a and b, weremeasured. The colour co-ordinates define the brightness and colour on acolour scale, where ‘a’ is a measure of redness (+a) or greenness (−a)and ‘b’ is a measure of yellowness (+b) or blueness (−b), (the moreyellow the coating, the higher the ‘b’ value). The co-ordinates ‘a’ and‘b’ approach zero for neutral colours (white, grays and blacks). Thehigher the values for ‘a’ and ‘b’ are, the more saturated a colour is.The lightness ‘L’ is measured on a scale from 0 (white) to 100 (black).

Yellowing in daylight is defined as the increase of the yellowness (dayΔb) of the coating during storage at 23±2° C. and in daylight for 28days. The yellowing in the dark is defined as the increase in theyellowness (dark Δb) of the coating during storage at 23±2° C. and inthe dark for 14 days.

Molecular Weight Determination

Gel permeation chromatography (GPC) analyses for the determination ofpolymer molecular weights were performed on an Alliance Waters 2690 GPCwith two consecutive PL-gel columns (type Mixed-C, I/d=300/7.5 mm) usingtetrahydrofuran (THF) as the eluent at 1 cm³/min and using an AllianceWaters 2410 refractive index detector. Samples corresponding to about 16mg of solid material were dissolved in 8 cm³ of THF, and the mixtureswere stirred until the samples had dissolved. The samples were leftundisturbed for at least 24 hours for complete “uncoiling” andsubsequently were filtered (Gelman Acrodisc 13 or 25 mm ø CR PTFE; 0.45μm) and placed on the auto-sampling unit of the GPC. A set ofpolystyrene standards (analysed according to DIN 55672) was used tocalibrate the GPC.

All species with a molecular weight less than 1000 Daltons are ignoredwhen calculating the Mw and PDi for the oligomers. When Daltons are usedin this application to give molecular weight data, it should beunderstood that this is not a true molecular weight, but a molecularweight measured against polystyrene standards as described above.

MATERIALS & ABBREVIATIONS USED

-   DEA=N,N-diethylethanolamine-   Cardura E10=Neodecanoic acid-2,3-epoxypropyl ester available from    Shell-   MPEG750=methoxypolyethylene glycol (Mn approximately 750)-   DMPA=dimethylolpropionic acid-   NMP=N-methylpyrrolidone-   TDI=toluene diisocyanate-   Dowanol DPM=dipropylene glycol monomethyl ether-   DAPRO5005=drier salt available from Profiltra-   1,4-CHDM=1,4-cyclohexanedimethanol-   Voranol P-400=polypropyleneglycol available from DOW Chemical-   A1310=NCO functional silane component available from CK Witco    Corporation-   DMBA=dibutylbutanoic acid-   TMPME=trimethylolpropanemonoallyl ether-   TMPDE=trimethylpropanediallylether-   IPDI=isophorone diisocyanate-   TEA=triethylamine-   Combi LS=drier salt available from Servo Delden-   Boltorn H20=Dendritic polymer available from Perstorp-   Nouracid LE80=linseed oil fatty acid available from AKZO Nobel-   Fastcat 2005=tin(II) chloride available from Elf-Atochem-   MEK=methyl ethyl ketone-   Atlas 4809=Alkyl phenol alkoxylate available from ATLAS Chemie-   Atpol E5720/20=Fatty alcohol ethoxylate available from Uniqema-   AP=ammonium persulphate-   Aerosol OT-75=Sodium dioctylsulphosuccinate available from Cytec-   MMA=methylmethacrylate-   n-BA=n-butylacrylate-   AA=acrylic acid-   SLS=Sodium Lauryl Sulphate-   Akyposal NAF=Sodium dodecylbenzenesulphonate available from KAO    Chemicals-   Natrosol 250LR=Hydroxy ethyl cellulose available from Hercules-   Akyporox OP-250V=Octyl phenol ethoxylate available from KAO    Chemicals-   Surfactant=Phosphate ester of nonyl phenol ethoxylate available from    KAO Chemicals-   VeoVa 10=Vinyl ester of versatic acid available from Shell-   Desmodur W=dicyclohexyl methane diisocyanate available from Bayer-   Priplast 3192=Dimeric acid polyester polyol available from Uniqema-   BMA=n-butyl methacrylate-   t-BHPO=t-butyl hydroperoxide-   Fe^(III).EDTA=ferric ethylene diamine tetracetic acid-   IAA=isoascorbic acid solution-   STY=Styrene-   2-EHA=2-Ethylhexylacrylate-   Dynasilan MEMO=3-Methacryloxypropyltrimethoxysilane available from    Degussa-   HEMA=Hydroxyethylmethacrylate-   TEGDMA=Triethyleneglycoldimethacrylate-   OMKT=n-octyl mercaptane-   TAPEH=tert-amylperoxy-2-ethyl hexanoate-   Water=demineralised water-   PW602=Transparent red iron-oxide pigment dispersion available from    Johnson Matthey-   AMP-95=2-amino-2-methyl-1-propanol (available from Intergrated    Chemicals bv)-   Delydran 1293=Defoamer additive (available from Cognis, 10% in BG)-   Sufynol 104E=Welting agent (available from Air Products, 50% in EG)-   NeoCryl BT-24=Acrylic emulsion polymer (available from NeoResins,    Avecia bv)    Preparation of an Alkyd Polyol Mixture X1

A 2-L round bottom flask, equipped with a stirrer and a thermometer, wasloaded with DEA; (247.56 g) and NaOMe (2.54 g). The mixture was heatedto 100° C. until the NaOMe was dissolved. Then sunflower oil (1248.08 g)was added giving a hazy reaction mixture. Stirring the hazy reactionmixture at 100 to 110° C. was continued until a clear reaction mixturewas obtained and a DEA-conversion of at least 85% was achieved, asdetermined by titration of residual amine functionality in the productwith aqueous HCl. The resulting mixture was then cooled to 70° C. beforeadding H₃PO₄ (1.81 g) and stirring for 15 minutes. The product mixture(X1) was cooled to room temperature and stored under nitrogen. The DEAconversion was 94%.

Preparation of Polyols X2 to X6:

The compositional details and the OH-values are given in Table 1 below.

Preparation of an Alkyd Polyol Mixture X2

Alkyd polyol X2 was prepared according to the same procedure as alkydpolyol X1 with the difference that the sunflower oil was replaced bytung oil.

Preparation of an Alkyd Polyol Mixture X3

The alkyd polyol X3 was prepared according to the same procedure asalkyd polyol mixture X1 with a different DEA/oil (mol/mol) ratio, 1.70instead of 1.60.

Preparation of Polyol X4

A 2-L reactor, equipped with a stirrer and a thermometer, was loadedwith Cardura E10 (1016.5 g), levulinic acid (483.4 g) anddimethylbenzylamine (4.5 g) in a nitrogen atmosphere. The temperaturewas raised to 140° C. and the mixture was stirred for 16 hours until anacid value of 1.2 was obtained. The product was cooled to roomtemperature and stored under nitrogen. The resulting OH value was 167.5mgKOH/g.

Preparation of an Poly-Alkoxylated Adduct X5

A 2-L 3-necked round bottom flask, equipped with stirrer, was loadedwith methoxypolyethylene glycol (MPEG750; 1323.53 g) and succinicanhydride (176.47 g) in a nitrogen atmosphere. The reaction mixture washeated to 120° C., and was stirred at this temperature until all theanhydride had reacted, as judged from the Infra Red spectrum of thereaction mixture (the anhydride groups typically show two absorptions at1785 cm⁻¹ and 1865 cm⁻¹, which disappeared and were replaced by a newester carbonyl absorption at 1740 cm⁻¹). The clear liquid product wasthen cooled to 50° C. and collected. The product solidified when leftundisturbed at ambient temperature. The resulting acid value was 68.7mgKOK/g and the resulting OH value was 100.0 mgKOH/g.

Preparation of an Alkyd Polyol Mixture X6

A 2-L 5-necked reactor flask fitted with a stirrer, a thermometer and acondenser fitted with a Dean-Stark condensate trap, was loaded withPentaerythritol (218.10 g), the levulinic acid (118.4 g), Prifac 8961-0(841.50 g) and Fastcat 2005 (0.50 g) in a nitrogen atmosphere. Thereaction mixture was heated to 210° C. for approximately 6 hours, untilan acid value of less than 1 mg KOH/g was obtained. The product wascooled to room temperature and stored under nitrogen.

TABLE 1 Composition (g) X1 X2 X3 DEA 247.56 939.39 287.3 NaOMe 2.54 9.33.54 Tung oil — 4739.88 — Sunflower oil 1248.08 — 1406.6 H₃PO₄ 1.81 6.602.53 OH-value (mg KOH/g) 264 264 270.5 DEA conversion  94%  92%  91%Preparation of Self-Crosslinkable (Autoxidisable) Urethane Oligomer A1,and its Dispersion DA1

A 1-L 3-necked round bottom flask, equipped with a stirrer and athermometer, was loaded with DMPA (19.36 g), NMP (92.5 g), 1,4-CHDM(8.97 g), MPEG750 (18.87 g) and the alkyd polyol mixture X1 (260.43 g)in a nitrogen atmosphere. The reaction mixture was stirred until a clearsolution was obtained. At a maximum temperature of 25° C. TDI (99.89 g)was fed into this reaction mixture without exceeding a reactortemperature of 50° C. After the TDI-feed was complete, the reactionmixture was heated to 80° C. and stirred at this temperature for 1 hour.The resultant NCO free alkyd urethane oligomer was then cooled to about70° C., and diluted with Dowanol DPM (51.38 g). Subsequently DMEA (10.27g) followed by the drier salt DAPRO5005 (5.84 g) was added and themixture was stirred for 15 minutes. Then water (155.43 g) was added andthe temperature was lowered to 55-60° C. The resultant predispersion wasstirred for an additional 15 minutes.

Part of the resultant predispersion (600 g), at 55 to 60° C., wasdispersed in water (752.889; 45-50° C.), over 60 minutes and under anitrogen atmosphere. While the predispersion is being dispersed, thetemperature of the water phase was 45 to 50° C. After the addition wascomplete, the final dispersion was stirred for an additional 15 minutes,cooled to 23° C., filtered over a 200-mesh sieve and stored undernitrogen. The dispersion DA1 had a solids content of 25 wt % and a pH of6.9.

The solution viscosity of a 80% solids solution of A1 in NMP (50° C.,shear rate 92.5 s⁻¹) is 10.9 Pa·s.

The solution viscosity of a 70% solids solution of A1 in NMP/H₂O/DMEA(2017/3) (23° C., shear rate 92.5 s⁻¹) is 6.6 Pa·s.

GPC analysis of A1: Mw=4917; PDi=1.94

Preparation of Self-Crosslinkable (Schiff-Base) Urethane Oligomer A2 andits Dispersion DA2

A 1-L 3-necked round bottom flask, equipped with a stirrer and athermometer, was loaded with DMPA (26.40 g), NMP (120.00 g), VoranolP-400 (198.01 g) and MPEG750 (22.22 g) in a nitrogen atmosphere. Thereaction mixture was stirred until a clear solution was obtained. Thepolyol mixture was fed to TDI (233.38 g) without exceeding a reactortemperature of 55° C. After the polyol-feed was complete, the reactionmixture was heated to 80° C. and stirred at this temperature for 1 hour.The NCO content of the obtained prepolymer was checked and was found tobe 8.94%. Subsequently the urethane prepolymer is capped with the polyolX4 (429.00 g). The temperature was raised to 100° C. The reactionmixture was kept at this temperature for 6.5 hours. Part of theresultant NCO free urethane oligomer (A2) (842.92 g) was cooled to 70°C., and diluted with Dowanol DPM (95.59 g) and NMP (87.87 g). Then DMEA(14.37 g) was added, and the resultant mixture was stirred for anadditional 15 minutes and cooled to 50° C. Part of the resultant mixture(600 g) was dispersed into water (831.00 g; 45 to 50° C.) under anitrogen atmosphere, over 60 minutes. Then the final dispersion wasstirred for an additional 15 minutes at 45 to 50° C., cooled to 23° C.,filtered over a 200-mesh sieve and stored under nitrogen.

The dispersion DA2 has a solids content of 29.6 wt % and a pH of 7.03.

The solution viscosity of an 80% solids solution of A2 in NMP (50° C.,shear rate 92.5 s⁻¹) was 30.0 Pa·s. The solution viscosity of a 70%solids solution of A2 in NMP/H₂O/DMEA (20/7/3) (23° C., shear rate 92.5s⁻¹) was 4.6 Pa·s.

GPC analysis of A2: Mw=3334; PDi=1.48.

Preparation of Self-Crosslinkable (Silane) Urethane Oligomer a3 and itsDispersion DA3

A 1-L 3-necked round bottom flask, equipped with a stirrer and athermometer, was loaded with DMPA (38.40 g), NMP (120.00 g), VoranolP-400 (285.38 g) and MPEG750 (22.22 g) in a nitrogen atmosphere. Thereaction mixture was stirred until a clear solution was obtained. At amaximum temperature of 25° C., TDI (134.00 g) was fed into this polyolmixture without exceeding a reactor temperature of 50° C. After theTDI-feed was complete, the reaction mixture was heated to 80° C. andstirred at this temperature for 1 hour. The resultant NCO free polymerwas then capped with A1310 (99.889), and diluted with NMP (25.00 g).Subsequently tin octoate (0.35 g) was added and the reactor temperaturewas raised to 90 to 95° C. The reaction mixture was kept at thistemperature for about 4 hours before cooling to 55 to 60° C. Part of theresultant silane functional urethane oligomer (563.10 g) was thendiluted with Dowanol DPM (57.80 g), neutralised with DMEA (19.80 g),homogenised for 15 minutes, and subsequently fed into water (860.62 g)in a separate reactor under a nitrogen atmosphere. The resultantdispersion was cooled to 23° C., filtered over a 200-mesh sieve andstored under nitrogen.

The dispersion DA3 had a solids content of 29.2% and a pH of 7.50.

The solution viscosity of an 80% solids solution of A3 in NMP (50° C.,shear rate 92.5 s⁻¹) was 37.0 Pa·s. The solution viscosity of a 70%solids solution of A3 in NMP/H₂O/DMEA (20/7/3) (23° C., shear rate 92.5s⁻¹) was 15.0 Pa·s. GPC analysis of A3: Mw=15401; PDi=2.40.

Preparation of Self-Crosslinkable (Autoxidisable) Urethane Oligomer A4,and its Dispersion DA4

A 2-L 3-necked round bottom flask, equipped with a stirrer and athermometer, was loaded with DMBA (48.00 g), NMP (240.00 g), TMPME(48.00 g), TMPDE (48.00 g), the alkydpolyol mixture X1 (497.10 g) andIPDI (318.90 g) in a nitrogen atmosphere. The reaction mixture wasslowly heated to 50° C. The tin octoate (0.40 g) was added and thereaction mixture was slowly heated until a reaction temperature of 90°C. is reached. This temperature was maintained for 4.5 hours. Theresultant urethane oligomer A4 was cooled to 70° C. A part of theoligomer (949.90 g) was diluted with Dowanol DPM (97.61 g), neutralisedwith triethylamine (TEA; 26.26 g) and subsequently Combi LS (47.50 g),followed by water (295.28 g), was added and homogenised forapproximately 15 minutes at 60° C. NMP (395.4 g) was added to theresultant predispersion to reduce the viscosity and homogenised furtherfor 15 minutes at 60° C. Part of the urethane predispersion (1100.00 g)was fed into water (889.3 g; 45 to 50° C.), in a separate reactor in anitrogen atmosphere, homogenised for an additional 15 minutes, cooled to23° C., filtered over a 200-mesh sieve, and stored in a nitrogenatmosphere. The resultant dispersion (DA4) had a solids content of 23.9%and a pH of 8.00.

The solution viscosity of an 80% solids solution of A4 in NMP (50° C.,shear rate 92.5 s⁻¹) was 14.0 Pa·s. The solution viscosity of a 70%solids solution of A4 in NMP/H₂O/DMEA (20/7/3) (23° C., shear rate 92.5s⁻¹) was 7.8 Pa·s.

GPC analysis of A4: Mw=4290; PDi=2.03.

Preparation of Self-Crosslinkable (Autoxidisable) Urethane Oligomer A5,and its Dispersion DA5

The alkyd urethane oligomer A5 and its dispersion DA5 were madeaccording to the same procedure as alkyd urethane oligomer A1 and itsdispersion DA1 except that alkyd polyol mixture X1 was replaced by alkydmixture X2 and Voranol P400. The oligomer details are listed in Table 2.The dispersion details are listed in Table 3.

Preparation of Self-Crosslinkable (Autoxidisable) Urethane Oligomer A6,and its Dispersion DA6

The alkyd urethane oligomer A6, and its dispersion were made accordingto the same procedure as alkyd urethane A1 and its dispersion DA1 exceptthat alkyd polyol mixture X1 was replaced by alkyd polyol mixture X3.The oligomer details are listed in Table 2. The dispersion details arelisted in Table 3.

Preparation of Self-Crosslinking (Autoxidisable) Hyperbranched PolyesterA7, and its Dispersion DA7

A 2-L 5-necked reactor flask fitted with a stirrer, a thermometer and acondenser fitted with a Dean-Stark condensate trap, was loaded withBoltorn H20 (150.00 g), adduct X5 (283.01 g) Nouracid (279.68 g) andFastcat 2005 (0.18 g) in a nitrogen atmosphere. The reaction mixture washeated to 230° C. and water was collected. The mixture was kept at 230°C. until an acid value of less than 10 mg KOH/g was obtained.

A portion of the resultant hyperbranched polyester A7 (250.00 g) washeated to 60° C. and diluted with NMP (62.50 g), Dowanol DPM (31.25 g)and finally Dapro 5005 (6.25 g) was added before dispersion by theaddition of water (50° C., 312.57 g) over a period of 10 minutes. Theresulting dispersion DA7 was stirred for an additional 30 minutes at 50°C. and subsequently cooled to 23° C. and stored in a nitrogenatmosphere.

The dispersion DA7, had a solids content of 37.85% and a pH of 7.03.

The solution viscosity of an 80% solids solution of A7 in NMP (50° C.,shear rate 91.9 s⁻¹) was 0.4 Pa·s. The solution viscosity of a 70%solids solution of A7 in NMP/H₂O/DMEA (20/7/3) (23° C., shear rate 91.9s⁻¹) was 1.7 Pa·s. GPC analysis of A7: Mw=19683; PDi=6.21.

Preparation of Self-Crosslinkable (Autoxidisable) Urethane Oligomer A8,and its Dispersion DA8

The urethane oligomer A8 and its dispersion DA8 were made according tothe same procedure as alkyd urethane A1 and its dispersion DA1 exceptthat a part of the alkyd polyol mixture X1 was replaced by the alkydpolyol mixture X2. The oligomer details are listed in Table 2. Thedispersion details are listed in Table 3.

Preparation of the Non-Crosslinkable Urethane Oligomer A9, and itsDispersion DA9

The alkyd urethane oligomer A9 and its dispersion DA9 were madeaccording to the same procedure as alkyd urethane oligomer A1 and itsdispersion DA1 except that the alkyd polyol mixture X1 was replaced byVoranol P-400. The oligomer details are listed in Table 2. Thedispersion details are listed in Table 3.

Preparation of a Self-Crosslinkable (Autoxidisable) Urethane OligomerA10 and its Dispersion DA10

The alkyd urethane oligomer A10 and its dispersion DA10 were madeaccording to the same procedure as alkyd urethane oligomer A1 and itsdispersion DA1 except that alkyd polyol mixture X1 was replaced by thealkyd polyol mixture X3, and the MPEG750 was removed. The oligomerdetails are listed in Table 2. The dispersion details are listed inTable 3.

Preparation of a Self-Crosslinkable (Autoxidisable) Urethane OligomerA11 and its Dispersion DA11

A 1-L 3-necked round bottom flask, equipped with a stirrer and athermometer, was loaded with DMPA (23.23 g), NMP (122.25 g), 1,4-CHDM(66.34 g), MPEG750 (22.64 g) and the alkyd polyol mixture X6 (25455 g)in a nitrogen atmosphere. The reaction mixture was stirred until a clearsolution was obtained. At a maximum temperature of 25° C. TDI (122.25 g)was fed into this reaction mixture without exceeding a reactortemperature of 50° C. After the TDI-feed was complete, the reactionmixture was heated to 80° C. and stirred at this temperature for 1 hour.An extra amount of NMP (40.75 g), and the resultant alkyd urethaneoligomer was then cooled to about 70° C., and further diluted withDowanol DPM (9.66 g). Subsequently DMEA (12.34 g) followed by the driersalt DAPRO5005 (7.00 g) was added and the mixture was stirred for 15minutes. Then water (186.51 g) was added and the temperature was loweredto 55-60° C. The resultant dispersion DA11 was stirred for an additional15 minutes, and stored under nitrogen.

The solution viscosity of a 80% solids solution of A11 in NMP (50° C.,shear rate 92.5 s⁻¹) is 17 Pa·s.

The solution viscosity of a 70% solids solution of A11 in NMP/H₂O/DMEA(2017/3) (23° C., shear rate 92.5 s⁻¹) is 21 Pa·s.

GPC analysis of A11: Mw=6954; PDi=2.48

Preparation of a Self-Crosslinkable (Autoxidisable) Urethane OligomerA12 and its Dispersion DA12

A 2-L 3-necked round bottom flask, equipped with a stirrer and athermometer, was loaded with DMBA (33.00 g), MPEG750 (27.78 g), thealkyd polyol mixture X1 (406.16 g), Tinoctoate (0.12 g) and IPDI (133.06g) in a nitrogen atmosphere. The reaction mixture was heated until areactor temperature of 100° C. was obtained. This temperature wasmaintained for 2 hours until no NCO was left. The resultant alkydurethane oligomer was then cooled to about 70° C. Subsequently TEA(17.28 g) followed by the drier salt DAPRO5005 (9.95 g), Combi LS (13.77g) and ATLAS G5000 (36.48 g) was added, and the mixture was stirred for15 minutes. Finally water (1296.34 g) was added to the prepolymer. Theresultant urethane dispersion had a solids content of 32.7% and a pH of7.6.

The solution viscosity of a 80% solids solution of A12 in NMP (50° C.,shear rate 92.5 s⁻¹) is 0.53 Pa·s.

The solution viscosity of a 70% solids solution of A12 in NMP/H₂O/DMEA(2017/3) (23° C., shear rate 92.5 s⁻¹) is 0.36 Pa·s.

GPC analysis of A13: Mw=1971; PDi=2.40.

TABLE 2 Components (g) A5 A6 A8 A9 A10 TDI 243.86 76.58 119.87 274.46363.50 DMPA 105.60 23.23 23.23 48.00 60.00 1,4-CHDM 0.00 10.76 10.760.00 — MPEG750 44.45 22.64 22.64 19.20 — Voranol P-400 362.09 — — 618.64— alkyd polyol X1 — — 156.25 — — alkyd polyol X2 204.00 — 156.25 — Alkydpolyol X3 — 355.79 — — 716.50 NMP 240.00 111.00 111.00 240.00 300.00Solution Viscosity* 23.0 0.5 24.0 57.0 255.0 Solution Viscosity** 12.50.9 10.2 36.7 343.4 Mw 5383 1948 5379 10251 172866 PDi 2.18 1.43 2.272.29 32.54 *80% solids in NMP at 92.5 s⁻¹ and 50° C. (Pa · s) **70%solids in NMP/H₂O/DMEA at 92.5 s⁻¹ and 23° C. (Pa · s)

TABLE 3 Composition DA5 DA6 DA8 DA9 DA10 Oligomer code A5 A6 A8 A9 A10Oligomer (g) 900.00 600.00 600.00 949.80 1440.00 DPM (g) 92.48 61.6661.72 97.60 150.00 DAPRO5005 (g) 10.50 7.00 7.01 11.08 16.80 DMEA (g)42.09 12.36 12.35 25.51 31.88 water (predispersion) (g) 279.99 186.51186.71 295.25 446.70 predispersion that is 1100.00 600.00 650.00 1100.00915.00 dispersed (g) water (g) 896.50 629.89 462.29 919.97 1575.58dispersion solids (%) 28.80 24.77 33.00 29.94 20.08 pH 6.20 6.10 7.107.70 7.70Preparation of Dispersed Vinyl Polymer P1

A 2-L 3-necked round bottom glass reactor, equipped with stirrer,thermometer and vortex breakers, was loaded with demineralised water(652.57 g), Atpol E5720/20 (4.99 g) and Borax.10H₂O (3.57 g) in anitrogen atmosphere. The mixture was heated whilst stirring to 80° C.and then a solution of AP (2.31 g) in demineralised water (16.00 g) wasadded. In a dropping funnel a pre-emulsion was prepared by stirring amixture of demineralised water (161.87 g), Atpol E5720/20 (94.85 g),Aerosol OT-75 (7.20 g), Borax.10H₂O (1.07 g), MMA (534.18 g), n-BA(444.32 g) and AA (19.97 g). 5% of this pre-emulsion was added to thereactor at 80° C. over 5 minutes. The remainder was fed into the reactorover 160 minutes at 85° C. A solution of AP (0.53 g) in demineralisedwater (7.88 g) was added to the reactor during the first 15 minutes offeeding the pre-emulsified feed. Then the reactor content was kept at85° C. for 30 minutes, and then cooled to 23° C. The pH was adjusted to8 to 8.5 with 12.5% aqueous ammonia. The resultant dispersed product(P1) was filtered and collected.

The properties of P1 are listed in Table 5.

Preparation of a Sequential Dispersed Vinyl Polymer P2

A 2-L 3-necked round bottom glass reactor, equipped with stirrer,thermometer and vortex breakers, was loaded with demineralised water(990.94 g), SLS (30%, 0.55 g) and NaHCO₃, (4.44 g) in a nitrogenatmosphere. The mixture was heated whilst stirring to 80° C. and then asolution of AP (0.89 g) in demineralised water (5.00 g) was added. In adropping funnel a monomer mixture was prepared by stirring MMA (140.48g), n-BA (207.71 g) and AA (7.11 g). 10% of this mixture was added tothe reactor at 80° C. The remainder was fed into the reactor over aperiod of 40 minutes at 85° C. The content of a separate droppingfunnel, containing demineralised water (20.00 g), AP (0.36 g) and SLS30% (11.62 g) was added in the same time. The reactor content was keptat 85° C. for 30 minutes. A second monomer mixture was prepared in adropping funnel consisting MMA (464.91 g), n-BA (57.37 g) and AA (10.66g). The mixture was fed to the reactor after the 30 minutes period in 60minutes. The content of a separate dropping funnel, containingdemineralised water (30.00 g), AP (0.53 g) and SLS 30% (17.44 g) wasadded in the same time. The reactor content was kept at 85° C. for 45minutes and then cooled to 23° C. The pH was adjusted to 8 to 8.5 with12.5% aqueous ammonia. The resultant product P2 was filtered andcollected.

The properties of P2 are listed in Table 5.

Preparation of Dispersed Vinyl Polymer P3

A 2-L 3-necked round bottom glass reactor, equipped with stirrer,thermometer and vortex breakers, was loaded with demineralised water(194.50 g), Akyposal NAF (3.00 g), Borax.10H₂O (1.25 g), Acetic acid(0.50 g) and Natrosol 250LR (10.00 g) in a nitrogen atmosphere. Themixture was heated whilst stirring to 60° C. and then a solution of AP(0.50 g) in demineralised water (10.00 g) was added. In a droppingfunnel a pre-emulsion was prepared by stirring with demineralised water(171.71 g), Akyposal NAF (3.00), Borax.10H₂O (1.25 g), Acetic acid (0.50g) and Akyporox OP-250V (14.29 g) followed by VeoVa 10 (125.00 g) andvinyl acetate (375.00 g). 10% of this mixture was added to the reactorat 60° C. The mixture was heated whilst stirring to 80° C. The remainderwas fed into the reactor over 90 minutes at 80° C. The content of aseparate dropping funnel, containing a solution of AP (1.15 g) indemineralised water (60.00 g), was added in the same time. Then thereactor content was kept at this temperature for 120 minutes and thencooled to 23° C. The pH was adjusted to 8 to 8.5 with 12.5% aqueousammonia. The resultant product P3 was filtered and collected.

The properties of P3 are listed in Table 5.

Preparation of the Dispersed Urethane Acrylic Polymer P4

Stage 1: A 1-L 3-necked round bottom flask, equipped with a stirrer anda thermometer, was loaded with NMP (100.00 g), DMPA (24.00 g), DesmodurW (152.68 g) and Priplast 3192 (223.33 g) in a nitrogen atmosphere. Thereaction mixture was heated to 55° C., tin octoate (0.05) was added andthe temperature was raised to 90-95° C. The mixture was kept at thistemperature for 1 hour before adding tinoctoate (0.05) and the mixturewas kept at 90° C. for an additional hour. The NCO-concentration of themixture was found to be 4.83%. The resulting NCO terminated urethaneprepolymer (500.05 g) (from which samples of a total weight of 10.0grams were taken for % NCO-determination, leaving 490.05 grams ofprepolymer) was then cooled to 70° C., neutralised with TEA (17.75 g)diluted with BMA (196.02 g) and homogenised for 15 minutes at 65° C.

Stage 2: A 2-L 3-necked round bottom flask, equipped with a stirrer andthermometer, was loaded with a water phase consisting of water (1045.77g) and BMA (174.00 g) in a nitrogen atmosphere. A portion of theurethane prepolymer (625.00 g) prepared in Stage 1 (at 60-65° C.) wasfed into the reactor over 1 hour, keeping the temperature of the reactorcontents below 30° C. After the feed was complete, the mixture wasstirred for an additional 5 minutes before chain-extension by theaddition of an aqueous 64.45% hydrazine hydrate solution (N₂H₄.H₂O,11.43 g in 25.00 g H₂O). A reactor temperature of 36° C. was reached.Subsequently, a 5% aqueous initiator solution of t-BHPO (18.10 g) and a1% aqueous solution of Fe^(III).EDTA; 4.63 g) was added to the reactionmixture. The radical polymerisation was started by the addition of a 1%aqueous iAA (45.24 g) and the reaction temperature was allowed to reach56° C. before more aqueous iAA (45.24 g) was added. The reaction mixturewas homogenised for 15 minutes, then cooled to 23° C., filtered over a200-mesh sieve and collected. The properties of P4 are listed in Table5.

Preparation of Dispersed Vinyl Polymer P5

A 2-L 3-necked round bottom glass reactor, equipped with stirrer,thermometer and baffles, was loaded with demineralised water (990.94 g),SLS 30% (0.55 g) and NaHCO₃ (4.44 g) in a nitrogen atmosphere. Themixture was heated whilst stirring to 80° C. and then a solution of AP(0.89 g) in demineralised water (5.00 g) was added. STY (468.54 g),2-EHA (361.69 g) and AA (58.00 g) were mixed in a dropping funnel. 10%of this mixture was added to the reactor at 80° C. and remainder was fedinto the reactor over 100 minutes at 85° C. The content of a separatedropping funnel, containing demineralised water (50.00 g), AP (0.89 g)and SLS 30% (29.06 g) was added in the same time and the reactor contentwas kept at 85° C. for 45 minutes and then cooled to 60° C. At 60° C. aburn-up was applied by adding a solution of iAA (2.60 g) indemineralised water (49.00 g) to the reactor followed by a mixture oft-BHPO (80%, 2.40 g) and demineralised water (18.00 g). After 60 minutesthe reactor content was cooled to 23° C. The pH was adjusted to 8 to 8.5with 12.5% aqueous ammonia. The product P5 was filtered and collected.The properties of P5 are listed in Table 5.

Preparation of Dispersed Polymers P6 to P11, P13 and P14

The dispersed polymers P6 to P11, P13 and P14 were prepared using themethod described for P5 with the variations as listed in Table 4. Theproperties of P6 to P11, P13 and P14 are listed in Table 5. P13 has aweight average molecular weight of 22097, a Mn of 10451 and a PDi of2.11. The Mn's and Mw's of P1 to P12 and P14 could not be measured.

Preparation of a Fatty Acid Functional Dispersed Polymer P12

In a 1 L 3-necked round bottom reactor, equipped with stirrer and N₂inlet, Nouracid LE80 (398.8 g), GMA (201.2 g), Irganox 1010 (0.10 g),Phenothiazine (0.10 g) and benzyl trimethylammonium hydroxide (40 wt %in water; 1.05 g) were loaded. The reactor was purged with nitrogen andthe yellow reaction mixture was heated and stirred at 155° C. until theacid value had dropped to 3.7 mg KOH/g. After cooling to ambienttemperature, the product was collected and stored under nitrogen.

A portion of 161.3 g of this adduct was mixed with MAA (40.3 g) andtransferred into a dropping funnel. This mixture was slowly added over aperiod of one hour to a 1 L 3-necked round bottom reactor containing asolution of lauroyl peroxide (21.4 g) in butyl glycol (273.0 g) at 125°C. in a nitrogen atmosphere. After complete addition, the resultingcopolymer solution was cooled to 50° C. and subsequently concentrated invacuo to 80% solids using a rotary evaporator. To the resulting yellowsolution, a mixture of water (580.0 g), aqueous ammonia (25%; 12.0 g)and SLS (4.4 g) was added at 70° C. A mixture of MMA (225.5 g) and BA(92.5 g) was added to the resulting dispersion and the reaction mixturewas stirred for 30 minutes at 70° C. The reaction mixture was heated to85° C. and a solution of ammonium persulphate (0.86 g) in water (20.0 g)was added over a period of 10 min. The mixture was stirred at 85° C. for3 h. Then a second portion of ammonium persulphate (0.86 g) in water(20.0 g) was added and the mixture was stirred at 85° C. for 30 minutes.Then a third portion of ammonium persulphate (0.86 g) in water (20.0 g)was added and the mixture was stirred for an additional 30 minutes at85° C. The resulting dispersion was cooled to 23° C., filtered andstored under nitrogen. The dispersion had a solids content of 39.3%, apH of 7.7 and contained 2.59% butyl glycol on total dispersion.

TABLE 4 Components (g) P6 P7 P8 P9 P10 P11 P13 P14 Reactor phase Water912.19 960.66 990.94 1001.24 960.66 990.94 1001.84 952.57 SLS 30% —72.94 0.55 — 72.94 0.55 — — Surfactant 0.83 — — — — — — 0.92 NaHCO₃ 4.124.38 4.44 4.46 4.38 4.44 4.39 4.57 Shot at 80° C. AP 0.83 0.88 0.89 0.890.88 0.89 0.88 0.92 Water 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.52Monomer mixture STY — — — — — 399.70 — — MMA 577.36 332.60 617.32 352.94759.26 124.35 346.07 611.55 BA 236.86 402.63 253.15 521.85 89.76 133.24511.70 239.02 BMA — — — — — 204.29 — — AA 16.62 17.77 17.85 17.51 17.777.51 18.29 MAA — 87.53 — — — — — — Dynasilan MEMO 41.54 — — — — — — —HEMA — 52.52 — — — — — — TEGDMA — — — — 8.75 — — — IOTG — — — — — —17.01 — AAEM — — — — — — — 45.73 Separate feed Water 50.00 50.00 50.0050.00 50.00 50.00 50.00 52.50 AP 0.83 0.88 0.89 0.89 0.88 0.89 0.88 0.92SLS 30% — — 29.06 14.88 — 29.06 14.59 — Surfactant 123.79 — — — — — —136.72 P11 only = Burn-up at 60° C. with IAA (0.88 g) water (12 g) tBHPO(0.88 g) and water (26.7 g)

TABLE 5 Parameter P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 P12 P13 P14 Solids[wt %] 51.2 45.1 50.3 35.2 42.4 44.6 21.4 45.0 45.0 44.6 44.3 39.3 44.544.5 pH 8.3 8.3 8.2 7.9 8.3 8.2 8.0 8.2 8.2 8.3 8.2 7.7 8.4 8.4 Particlesize [nm] 450 230 330 65 255 390 69 307 590 67 230 — 350 406 MeasuredTg* 25 2 24 43 27 58 40 57 2 96 54 49 −7 51 [° C.] Acid value** 15.615.6 0 12.4 50.6 15.6 63.4 15.6 15.6 15.6 15.6 — 15.6 15.6 *with DSC(midpoint) **Theoretical on solids [mgKOH/g]Preparation of blends of the dispersed oligomers and dispersed polymersprepared above: The compositional details and properties are listed inTable 6 below.Preparation of a Blend of Dispersed Oligomer DA1 and Dispersed PolymerP1=A1P1

A 500-mL 3-necked round bottom flask, equipped with a stirrer, wasloaded with DA1 (206.60 g) in a nitrogen atmosphere, then P1 (97.60 g)followed by water (95.66 g) was added while stirring the mixture. Theblend was stirred for an additional 20 minutes at room temperature andthen stored under nitrogen. The blend had a solids content of 25 wt %,and a pH of 6.9.

Preparation of Blends A1P2, A1P3. A1P4, A3P6, A4P7, A5P8, A6P9, A10P1,A12P1 and A1P12

The blends were made according to the same procedure as blend dispersionA1P1, except that no additional water was added, and details are shownin Table 6 below.

Preparation of Blend A2P5

A 500-mL jar was loaded with DA2 (315.00 g) and adipic dihydrazide(10.01 g) in a nitrogen atmosphere and homogenised. Then P5 (88.56 g)was added while stirring the mixture. The blend was stirred for anadditional 20 minutes at room temperature and then stored undernitrogen. The blend had a solids content of 32.6 wt %, and a pH of 8.2

Preparation of Blend A3A7P10

A 2-L round bottom flask, equipped with a stirrer, was loaded with DA3(228.22 g) and DA7 (771.78 g) in a nitrogen atmosphere and homogenisedat room temperature. Part of this (BA3A7, 225.00 g), was blended withP10 (122.03 g) and water (41.64 g) and homogenised at room temperatureand the blend A3A7P10 was stored under nitrogen. The blend had a solidscontent of 35 wt %, and a pH of 7.2.

Preparation of Blend A3A8A9P11

A 1-L round bottom flask, equipped with a stirrer, was loaded with DA3(157.14 g) and DA8 (142.86 g) in a nitrogen atmosphere and homogenisedat room temperature. A

Preparation of Blend A3A8A9P11

A 1-L round bottom flask, equipped with a stirrer, was loaded with DA3(157.14 g) and DA8 (142.86 g) in a nitrogen atmosphere and homogenisedat room temperature. A part of this blend (A3A8, 272.21 g) was blendedwith DA9 (427.79 g) and then a part of this blend (A3A8A9, 270.00 g) wasblended with P11 (124.16 g), homogenised at room temperature and storedunder nitrogen. The blend had a solids content of 34.89 wt %, and a pHof 7.4.

Preparation of Blend A11P12

A 500-mL 3-necked round bottom flask, equipped with a stirrer andthermometer was loaded with P12 (140.70 g) in a nitrogen atmosphere, andthen heated to 50° C. Subsequently urethane oligomer A11 (100.00 g),which was conditioned at a temperature of 55° C., was fed into thedispersed polymer over a 30 minute period, without exceeding a reactortemperature of 50° C. The batch was cooled to room temperature, afterwater (24.35 g), and ADH (2.21 g) was added, while the dispersion wasstirred. After the batch was mixed for an extra 15 minutes, the batchwas filtered over a 200-mesh sieve and collected. The blend has solidscontent of 41.8% and a pH of 6.8.

TABLE 6 A1P2 A1P3 A1P4 A3P6 A4P7 A5P8 A6P9 A10P1 A1P12 A12P1 OligomerDA1 DA1 DA1 DA3 DA4 DA5 DA6 DA10 DA1 DA13 Oligomer (g) 225.00 270.00225.00 270.00 150.00 200.00 90.00 100.00 200.00 150.00 Oligomer 50.0050.00 50.00 60.00 40.00 40.00 15.00 50.00 50.00 50.00 (% of solids)Polymer P2 P3 P4 P6 P7 P8 P9 P1 P13 P1 Polymer (g) 120.75 129.96 154.65117.90 259.46 192.00 295.20 39.22 111.7 95.8 Polymer 50.00 50.00 50.0040.00 60.00 60.00 85.00 50.00 50 50 (% of solids) Blend solids 31.5032.70 28.70 33.90 23.40 36.74 40.60 28.85 31.9 39.9 (wt %) pH 7.3 7.07.2 7.4 7.7 6.2 7.8 7.5 6.9 7.7

EXAMPLE 1 Pigmented Paint Composition Comprising Urethane Oligomer A1

A 500-mL jar, equipped with a stirrer, was loaded with A1 (300 g) andC830 a TiO₂-based pigment paste (89.37 g; solids content of 74.9%) in anitrogen atmosphere, and the mixture was stirred for 30 minutes atambient temperature. The resulting paint formulation had a solidscontent of 35.84%. Then a wetting agent (Byk 344, 0.90 g) was addedfollowed by a thickener (Borchigel LM75, available from Bayer) until aviscosity of 4000 to 6000 mPa·s was reached. The paint formulation wasleft undisturbed for 24 h, then stirred up to mix the contentsintimately, checked (and when necessary corrected) for its viscosity.

Pigment paste C830 comprised TiO₂ (24.0 g), propylene glycol (2.4 g),water (3.3 g), AMP-95 (0.2 g), Dehydran 1293 (0.5 g), Surfinol 104E (0.4g) and NeoCryl BT-24 (3.1 g).

EXAMPLES 2 TO 7a, 8 TO 13

Examples 2 to 7a and 8 to 13 were prepared with the variations andphysical properties as listed in Table 7 below using the methoddescribed above for Example 1, except that for Example 11b PW602 wasused instead of C830.

EXAMPLE 7b Clear Composition Comprising Blend A3P6

A 500-mL jar, equipped with a stirrer was loaded with blend A3P6 (300.00g) in a nitrogen atmosphere. Byk 344 (0.90 g) was added followed byBorchigel LM75 until a viscosity of 4000 to 6000 mPa·s was obtained.

Water Resistance:

The water resistance level for Examples 2 and 5 were 5 before recoveryand 5 after recovery.

Detergent Resistance:

The detergent resistance level for Example 7a 5 before recovery and 5after recovery.

COMPARATIVE EXAMPLES 14 to 18

Comparative paint compositions were prepared using the method describedabove for example 1 with the variations and physical properties aslisted in Table 7 below, except that for Example C18 PW602 was usedinstead of C830.

COMPARATIVE EXAMPLE C19 (CLEAR)

A 500-mL jar, equipped with a stirrer was loaded with P5 (150.0 g) andbutyl glycol (12.72 g) in nitrogen atmosphere, followed by BorchigelLM75 until a viscosity of 4000 to 6000 mPa·s was obtained.

COMPARATIVE EXAMPLE C20 (CLEAR)

P7 was used as prepared above with no additional formulation.

TABLE 7 EXAMPLE 1 2 3 4 5 6 7a Dispersion DA1 A1P1 A1P2 A1P3 A1P4 A2P5A3P6 Dispersion (g) 300 300 300 300 300 300 300 Pigment paste TiO₂ (g)89.37 92.32 116.32 120.76 106 120.4 125.2 Solids (wt %) 36.4 36.7 43.644.8 40.8 44.7 46.0 Open Time (mins) 50 60 60 48 60 46 32 Wet edge time(mins) 32 25 12 16 24 12 20 Dust-free time (hours) 3.5 1 1.5 2.5 1.25 22 Tack-free time (hours) 9 <15 5 <15 15 15 15 Thumb-hard time (hours) —15.5 9 15 20 20 23 Sandability time (hours) — 22 16 — 16 16 22 Yellowing(dark Δb) 3.5 2.5 2.2 2.5 2.4 0.3 0.3 Yellowing (day Δb) 1.4 0.9 0.651.05 1.1 0.5 0.3 EXAMPLE 7b 8 9 10 11a 11b 12 Dispersion A3P6 A4P7 A5P8A6P9 A3A7P10 A3A7P10 A3A8A9 P11 Dispersion (g) 300 300 250 250 240 240250 Pigment paste TiO₂ (g) — 83.4 112.93 124.83 107.2 PW602, 107.37 9.6Solids (wt %) 33.9 34.0 48.6 52.0 47.3 35.5 46.9 Open Time (mins) 36.537 52 44 60 40 28 Wet edge time (mins) 23.5 15 24 20 24 21 14 Dust-freetime (hours) 3.5 0.75 1.3 1 1.5 1.25 1.25 Tack-free time (hours) 15 <1519 19 8 8 15 Thumb-hard time (hours) 24 15.5 22 23 17.5 17 22Sandability time (hours) — — — — 16 — 22 Yellowing (dark Δb) — 1.2 2.71.8 2.5 — 1.6 Yellowing (day Δb) — 0.8 1.4 1.3 0.0 — 1.1 EXAMPLE 13 C14C15 C16 C17 C18 C19 C20 Dispersion A11P12 DA10 A10P1 P1 A1P13 A12P1 P5P7 Dispersion (g) 120 300 100 200 200 200 150 100 Pigment paste TiO₂ (g)62.04 74.16 35.5 126 78.5 PW602, — — 8.0 Solids (wt %) 53.2 30.3 40.960.4 44.01 40.2 39.1 21.4 Open Time (mins) 42 50 47 9 50 50 35 45 Wetedge time (mins) 14 7 8 4 24 25 7 8 Dust-free time (hours) 1 3 0.5 0.251.5 0.75 15 30 Tack-free time (hours) 8 6 4.5 0.5 7 19 1.5 0.5Thumb-hard time (hours) <16 — — 0.5 8.5 — 2 1 Sandability time (hours)5.8 — — — — — — — Yellowing (dark Δb) 6.6 1.4 3.1 0.3 4.5 — — —Yellowing (day Δb) — 0.0 1.3 0.3 — 3.5 — —Equilibrium Viscosities were Measured for the Examples Listed Below inTables 8 to 29.

TABLE 8 Example 1: Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity Viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)2.0 37.04 16 14 9  7 14.0 40.97 52 28 18  7 30.0 47.27 394 258 74 — 34.049.27 1770 456 259 — 40.0 52.32 1840 471 259 — 43.5 54.24 821 168 52 —50.0 57.7 883 178 54 — 57.0 61.9 1770 192 40 — 63.5 64.93 1700 193 42 2069.0 66.43 2080 226 47 21

TABLE 9 Example 2 Shear rate Shear rate Shear rate Shear rate 0.0997 s⁻¹0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)1.5 37.62 67 20 11  4 8.5 40.38 118 28 15 — 14.5 43.07 152 47 26  7 21.046.33 174 73 34 13 28.5 50.53 225 100 61 — 31.5 52.34 308 149 83 — 36.555.53 535 265 94 — 39.5 57.55 925 368 — — 40.0 60.71 2050 516 106  —44.0 62.91 2510 562 112  —

TABLE 10 Example 3: Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)3.0 45.22 176  46 17  7 11.0 48.71 358  65 26 10 22.0 53.91 513 103 5215 28.5 57.22 427 159 70 — 35.0 60.69 1630 363 75 — 40.0 63.48 2460 515— — 46.0 66.95 2390 492 105  — 52.0 70.57 11100 — — —

TABLE 11 Example 4: Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)1.0 45.01 126 23 11 4 7.0 47.50 113 25 13 5 13.0 50.14 235 44 22 9 17.552.21 153 52 27 11  24.0 55.36 275 104 48 19  28.0 57.39 337 134 56 —34.0 60.57 1530 303 76 — 39.0 63.36 2520 482 117  — 46.0 67.48 182003890 285  — 52.0 71.22 30800 8070 — — 57.0 74.50 28000 — — —

TABLE 12 Example 5: Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)0.0 41.06 187 50 17 8 7.0 43.17 275 54 21 9 13.0 45.22 424 92 35 13 19.047.47 727 163 53 17 23.5 49.29 594 152 50 129 30.0 52.13 1920 543 122 —34.5 54.25 3160 699 165 — 40.0 56.99 6840 1030 255 44.0 59.09 9840 1520300 — 50.0 62.42 41100 — — —

TABLE 13 Example 6: Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)2.0 45.83 74 34 16 — 14.0 51.09 77 32 16 10 18.0 52.76 85 42 22 12 24.055.28 111 55 30 — 29.0 57.44 165 77 40 — 39.0 61.82 425 134 58 — 47.065.15 4130 663 163 — 53.0 67.25 7290 1170 208 — 58.0 68.56 2260 435 —

TABLE 14 Example 7a: Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)3.0 47.00 52 24 9  5 12.0 51.92 124 41 18  7 22.0 57.40 253 58 29 1427.0 60.13 413 111 55 17 34.0 63.96 468 123 64 — 37.0 65.60 1120 244 107— 45.0 69.98 2650 526 132 — 49.0 72.17 3860 807 184 —

TABLE 15 Example 7b: Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)1.5 34.53 5 14 5 — 12.5 38.69 6 9 9  7 23.0 42.89 40 31 17 11 32.0 46.7662 52 41 — 43.0 51.72 162 114 80 — 47.5 53.73 201 140 95 — 57.0 57.67294 191 123 — 62.5 59.58 531 267 169 — 68.0 61.06 826 367 202 — 72.561.85 3320 1060 576 —

TABLE 16 Example 8: Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)1.5 34.2 37 10 5 2 7.0 35.2 — 14 7 3 17.0 37.2 56 16 6 2 27.5 39.4 31868 21 — 36.0 41.5 390 136 39 17 52.0 45.0 2160 612 — — 56.5 46.1 1670434 126 — 62.5 47.6 1020 256 67 — 67.5 48.9 1170 244 — — 85.5 53.8 3410677 — — 92.5 55.8 4490 — — — 94.0 56.3 15000 — — —

TABLE 17 Example 9: Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)1.5 49.24 78 10 2 1 6.5 51.61 70 10 3 1 12.0 54.28 94 15 4 2 20.0 58.26209 24 5 2 30.0 63.53 868 120 20 7 33.0 65.14 1340 154 25 8 38.5 68.162220 246 34 — 42.0 70.12 3030 378 55 — 47.0 72.97 4920 768 93 — 49.574.42 6790 925 — —

TABLE 18 Example 10: Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)2.5 53.23 234 38  11 4 7.0 55.75 275 72  22 8 13.0 59.25 750 132  40 —18.5 62.60 849 249  75 — 25.0 66.71 1380 414 130 — 32.5 71.68 2590 620 —— 37.5 75.12 7210 1150 266 — 43.5 79.39 29700 — — —

TABLE 19 Example 11a: Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)2.0 48.47 222 34 9 4 6.5 51.38 — 33 12 6 12.0 54.92 259 63 19 9 15.056.87 364 63 21 10 20.0 60.28 433 86 29 13 24.0 62.81 718 160 52 20 28.065.99 1450 350 102 — 32.0 69.03 4330 1150 222 — 37.0 72.69 8670 2160 372— 40.5 74.42 15800 3380 535 —

TABLE 20 Example 11b: Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)1.00 35.5 40 17  7  4 8.50 37.5 140 37 12  7 17.00 40.5 238 73 19  726.00 44.5 265 80 19 15 33.00 48.2 645 182 48 — 39.50 52.1 1570 352 — —43.00 54.4 2330 622 — — 46.00 56.4 3510 848 — — 51.00 60.1 4310 958 — —53.00 61.6 5340 1140 — —

TABLE 21 Example 12: Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)2.0 47.70 49 31 11 6 8.5 50.56 90 32 15 9 17.0 54.65 178 56 32 15 19.055.67 301 77 40 — 25.0 58.87 474 124 60 — 29.0 61.11 666 176 78 — 34.064.04 1110 242 88 — 37.0 65.87 1520 300 — — 42.0 69.03 4240 671 — — 46.071.65 12900 1540 — —

TABLE 22 Example 13: Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)2.0 54.19 52 23 9  5 7.0 56.08 217 27 12 — 13.0 58.33 322 65 24 11 18.060.22 660 101 35 14 24.0 62.47 1550 440 116 — 28.0 63.98 4360 1010 130 —33.0 65.86 10800 2190 — — 36.0 66.99 20500 3640 — —

TABLE 23 Example C14: Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)2.5 31.56 270 85 19 3 15.0 34.96 319 140 32 6 23.5 37.71 557 201 50 —30.5 40.25 822 262 66 — 36.5 42.62 1850 427 96 — 41.5 44.73 3300 618 121— 47.5 47.44 5620 1020 — — 53.5 50.32 6170 1120 — —

TABLE 24 Example C15 Shear rate Shear rate Shear rate 0.0997 s⁻¹ 0.990s⁻¹ 9.97 s⁻¹ Time Calculated viscosity viscosity viscosity (min) Solids(%) (Pa · s) (Pa · s) (Pa · s) 1.5 41.4 231 43  16 6.0 42.68 391 93  3212.5 44.4 724 201  63 17.0 45.95 1960 318 — 23.5 47.96 1520 559 133 27.549.33 2230 836 — 33.0 51.41 2180 1050 — 37.5 53.15 5140 2150 —

TABLE 25 Example C16: Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)0.50 61.21 1650  54 23 5.98 6.00 64.24 2220 161 — — 10.00 66.44 2510 203— — 13.00 68.09 4280 360 — — 21.00 72.49 5830 — — —

TABLE 26 Example C17: Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)4.00 45.37 38 21 14 8 13.00 48.20 60 31 22 — 23.00 51.53 — 45 30 — 28.0053.35 102 61 — — 37.50 57.16 265 118 41 — 44.50 60.25 288 144 57 — 53.0064.21 667 268 — — 57.00 66.10 645 255 — — 67.00 70.67 1150 314 — — 76.0074.18 2340 389 — — 85.00 76.55 38500 — — —

TABLE 27 Example C18: Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)4.00 41.83 41 26 10 2 9.00 43.65 55 36 15 3 13.00 45.02 85 48 18 4 18.0046.74 117 58 20 4 24.00 49.01 170 72 23 — 30.00 51.66 284 87 28 — 34.0053.69 309 92 30 6 38.00 55.95 344 88 33 — 44.00 57.46 359 81 — — 49.0060.33 327 72 — — 54.00 63.46 396 94 34 — 59.00 66.62 268 96 40 6 70.0074.40 259 121 54 11  75.00 77.60 850 188 75 — 78.00 79.19 — — — — 83.0081.31 5070 604 — —

TABLE 28 Example C19 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)3.0 41.74 506 104 16 3 9.0 46.28 1465 341 59 13 14.5 50.99 5043 1334 30551 23.0 59.16 16240 5356 910 193 29.0 65.50 22290 12750 2040 448

TABLE 29 Example C20 Shear rate Shear rate Shear rate Shear rate 0.0997s⁻¹ 0.990 s⁻¹ 9.97 s⁻¹ 78.6 s⁻¹ Time Calculated viscosity viscosityviscosity viscosity (min) Solids (%) (Pa · s) (Pa · s) (Pa · s) (Pa · s)0. 22.20 68 28 10 3 5.0 24.03 120 56 18 4 12.0 26.54 1156 422 82 15 18.028.93 5804 1588 212 33 24.0 31.81 8118 2073 289 69 31.0 36.13 12560 4273568 116 38.0 41.88 12720 3278 415 78 44.0 48.27 33020 8738 1087 186

1. An aqueous coating composition comprising a physical blend of acrosslinkable water-dispersible polyurethane oligomer(s) and 10 to 56 wt% of a dispersed vinyl polymer, 0 to 25% of co-solvent by weight of thecomposition, said polyurethane oligomer(s) having: a) a measured weightaverage molecular weight in the range of from 1,500 to 50,000 Daltons;and b) a solution viscosity ≦150 Pa·s, as determined from an 80% byweight solids solution of the crosslinkable polyurethane oligomer(s) inat least one of the solvents selected from the group consisting ofN-methylpyrrolidone, n-butylglycol and mixtures thereof, using a shearrate of 90±5 s⁻¹ and at 50±2° C.; and said dispersed vinyl polymer(s)having: a) a measured weight average molecular weight ≧90,000 Daltons;and b) an acid value up to 100 mgKOH/g; said composition when drying toform a coating having the following properties: i) an open time of atleast 20 minutes; ii) a wet edge time of at least 10 minutes; iii) atack-free time of ≦20 hours; iv) an equilibrium viscosity of ≦5,000Pa·s, at any solids content when drying in the range of from 20 to 55%by weight of the composition, using any shear rate in the range of from9±0.5 to 90±5 s⁻¹ and at 23+2° C.; and wherein the crosslinkablewater-dispersible polyurethane oligomer(s) is crosslinkable byautooxidation optionally in combination with silane or Schiff basecondensation.
 2. An aqueous coating composition according to claim 1wherein said polyurethane oligomer(s) has a solution viscosity ≦250Pa·s, as determined from a 70% by weight solids solution of thecrosslinkable polyurethane oligomer(s) in a solvent mixture consistingof: i) at least one of the solvents selected from the group consistingof N-methylpyrrolidone, n-butylglycol and mixtures thereof; ii) waterand iii) N,N-dimethylethanolamine; where i), ii) and iii) are in weightratios of 20/7/3 respectively, using a shear rate of 90±5 s⁻¹ and at23±2° C.
 3. An aqueous coating composition comprising a physical blendof a crosslinkable water-dispersible polyurethane oligomer(s) which iscrosslinkable by autooxidation and 10 to 56 wt % of a dispersedpolymer(s) and 0 to 25% of co-solvent by weight of the composition, saidcrosslinkable water-dispersible polyurethane oligomer(s) having: a) ameasured weight average molecular weight in the range of from 1,500 to50,000 Daltons; and b) a solution viscosity ≦150 Pa·s, as determinedfrom an 80% by weight solids solution of the crosslinkablewater-dispersible polyurethane oligomer(s) in at least one of thesolvents selected from the group consisting of N-methylpyrrolidone,n-butylglycol and mixtures thereof, using a shear rate of 90±5 s⁻¹ andat 50±2° C.; and said dispersed polymer(s) having: a) a measured weightaverage molecular weight ≧90,000 Daltons; and b) an acid value up to 100mgKOH/g; wherein said composition when drying to form a coating has thefollowing properties: i) an open time of at least 20 minutes; ii) a wetedge time of at least 10 minutes; iii) a tack-free time of ≦20 hours;and iv) an equilibrium viscosity of ≦5,000 Pa·s, at any solids contentwhen drying in the range of from 20 to 55% by weight of the composition,using any shear rate in the range of from 9±0.5 to 90±5 s⁻¹ and at 23±2°C.
 4. An aqueous composition according to claim 3 wherein thecrosslinkable water-dispersible polyurethane oligomer(s) containsautooxidisable groups and carbonyl functional groups.
 5. An aqueouscoating composition comprising a physical blend of a crosslinkablewater-dispersible polyurethane oligomer(s) which is crosslinkable byautooxidation and a dispersed polymer(s) in a ratio by weight of 90:10to 10:90, and 0 to 25% of co-solvent by weight of the composition, saidpolyurethane oligomer(s): a) having a measured weight average molecularweight in the range of from 1,500 to 50,000 Daltons; b) having asolution viscosity ≦150 Pa·s, as determined from an 80% by weight solidssolution of the crosslinkable polyurethane oligomer(s) in at least oneof the solvents selected from the group consisting ofN-methylpyrrolidone, n-butylglycol and mixtures thereof, using a shearrate of 90±5 s⁻¹ and at 50±2° C.; and c) being obtained by capping anisocyanate-terminated polyurethane oligomer with a monofunctionalisocyanate-reactive compound and/or by using a stoichlometric excess ofreactants having isocyanate-reactive groups during the oligomerpreparation; said dispersed polymer(s) having: a) a measured weightaverage molecular weight ≧90,000 Daltons; and b) an acid value up to 100mgKOH/g; wherein said composition when drying to form a coating has thefollowing properties: i) an open time of at least 20 minutes; ii) a wetedge time of at least 10 minutes; iii) a tack-free time of ≦20 hours;iv) an equilibrium viscosity of ≦5,000 Pa·s, at any solids content whendrying in the range of from 20 to 55% by weight of the composition,using any shear rate in the range of from 9±0.5 to 90±5 s⁻¹ and at 23±2°C.